Emacs lisp function to select a HTML entity from a filterable list and insert it at point. Based on Based on code by @emacs_gifs from https://emacsgifs.github.io/html-entities-helper

html-entity-insert.el

;; Licensed under GNU/GPL. https://emacsgifs.github.io/html-entities-helper
(defun ct/html-entity-insert ()
    "Select and insert an html entity.
Uses the list from https://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references."
    (interactive)
    (defvar _html-entity-list
      '("char: \" entity: "    text: quotation mark (APL quote)"
        "char: & entity: &      text: ampersand"
        "char: ' entity: '     text: apostrophe (apostrophe-quote); see below"
        "char: < entity: &lt;       text: less-than sign"
        "char: > entity: &gt;       text: greater-than sign"
        "char:   entity: &nbsp;     text: no-break space (non-breaking space)[d]"
        "char: ¡ entity: &iexcl;    text: inverted exclamation mark"
        "char: ¢ entity: &cent;     text: cent sign"
        "char: £ entity: &pound;    text: pound sign"
        "char: ¤ entity: &curren;   text: currency sign"
        "char: ¥ entity: &yen;      text: yen sign (yuan sign)"
        "char: ¦ entity: &brvbar;   text: broken bar (broken vertical bar)"
        "char: § entity: &sect;     text: section sign"
        "char: | entity: &#124;     text: vertical bar (unix pipe)"
        "char: ¨ entity: &uml;      text: diaeresis (spacing diaeresis); see Germanic umlaut"
        "char: © entity: &copy;     text: copyright symbol"
        "char: ª entity: &ordf;     text: feminine ordinal indicator"
        "char: « entity: &laquo;    text: left-pointing double angle quotation mark (left pointing guillemet)"
        "char: ¬ entity: &not;      text: not sign"
        "char:   entity: &shy;      text: soft hyphen (discretionary hyphen)"
        "char: ® entity: &reg;      text: registered sign (registered trademark symbol)"
        "char: ¯ entity: &macr;     text: macron (spacing macron, overline, APL overbar)"
        "char: ° entity: &deg;      text: degree symbol"
        "char: ± entity: &plusmn;   text: plus-minus sign (plus-or-minus sign)"
        "char: ² entity: &sup2;     text: superscript two (superscript digit two, squared)"
        "char: ³ entity: &sup3;     text: superscript three (superscript digit three, cubed)"
        "char: ´ entity: &acute;    text: acute accent (spacing acute)"
        "char: µ entity: &micro;    text: micro sign"
        "char: ¶ entity: &para;     text: pilcrow sign (paragraph sign)"
        "char: · entity: &middot;   text: middle dot (Georgian comma, Greek middle dot)"
        "char: ¸ entity: &cedil;    text: cedilla (spacing cedilla)"
        "char: ¹ entity: &sup1;     text: superscript one (superscript digit one)"
        "char: º entity: &ordm;     text: masculine ordinal indicator"
        "char: » entity: &raquo;    text: right-pointing double angle quotation mark (right pointing guillemet)"
        "char: ¼ entity: &frac14;   text: vulgar fraction one quarter (fraction one quarter)"
        "char: ½ entity: &frac12;   text: vulgar fraction one half (fraction one half)"
        "char: ¾ entity: &frac34;   text: vulgar fraction three quarters (fraction three quarters)"
        "char: ¿ entity: &iquest;   text: inverted question mark (turned question mark)"
        "char: ` entity: &#96;      text: grave accent"
        "char: À entity: &Agrave;   text: Latin capital letter A with grave accent (Latin capital letter A grave)"
        "char: Á entity: &Aacute;   text: Latin capital letter A with acute accent"
        "char: Â entity: &Acirc;    text: Latin capital letter A with circumflex"
        "char: Ã entity: &Atilde;   text: Latin capital letter A with tilde"
        "char: Ä entity: &Auml;     text: Latin capital letter A with diaeresis"
        "char: Å entity: &Aring;    text: Latin capital letter A with ring above (Latin capital letter A ring)"
        "char: Æ entity: &AElig;    text: Latin capital letter AE (Latin capital ligature AE)"
        "char: Ç entity: &Ccedil;   text: Latin capital letter C with cedilla"
        "char: È entity: &Egrave;   text: Latin capital letter E with grave accent"
        "char: É entity: &Eacute;   text: Latin capital letter E with acute accent"
        "char: Ê entity: &Ecirc;    text: Latin capital letter E with circumflex"
        "char: Ë entity: &Euml;     text: Latin capital letter E with diaeresis"
        "char: Ì entity: &Igrave;   text: Latin capital letter I with grave accent"
        "char: Í entity: &Iacute;   text: Latin capital letter I with acute accent"
        "char: Î entity: &Icirc;    text: Latin capital letter I with circumflex"
        "char: Ï entity: &Iuml;     text: Latin capital letter I with diaeresis"
        "char: Ð entity: &ETH;      text: Latin capital letter Eth"
        "char: Ñ entity: &Ntilde;   text: Latin capital letter N with tilde"
        "char: Ò entity: &Ograve;   text: Latin capital letter O with grave accent"
        "char: Ó entity: &Oacute;   text: Latin capital letter O with acute accent"
        "char: Ô entity: &Ocirc;    text: Latin capital letter O with circumflex"
        "char: Õ entity: &Otilde;   text: Latin capital letter O with tilde"
        "char: Ö entity: &Ouml;     text: Latin capital letter O with diaeresis"
        "char: × entity: &times;    text: multiplication sign"
        "char: Ø entity: &Oslash;   text: Latin capital letter O with stroke (Latin capital letter O slash)"
        "char: Ù entity: &Ugrave;   text: Latin capital letter U with grave accent"
        "char: Ú entity: &Uacute;   text: Latin capital letter U with acute accent"
        "char: Û entity: &Ucirc;    text: Latin capital letter U with circumflex"
        "char: Ü entity: &Uuml;     text: Latin capital letter U with diaeresis"
        "char: Ý entity: &Yacute;   text: Latin capital letter Y with acute accent"
        "char: Þ entity: &THORN;    text: Latin capital letter THORN"
        "char: ß entity: &szlig;    text: Latin small letter sharp s (ess-zed); see German Eszett"
        "char: à entity: &agrave;   text: Latin small letter a with grave accent"
        "char: á entity: &aacute;   text: Latin small letter a with acute accent"
        "char: â entity: &acirc;    text: Latin small letter a with circumflex"
        "char: ã entity: &atilde;   text: Latin small letter a with tilde"
        "char: ä entity: &auml;     text: Latin small letter a with diaeresis"
        "char: å entity: &aring;    text: Latin small letter a with ring above"
        "char: æ entity: &aelig;    text: Latin small letter ae (Latin small ligature ae)"
        "char: ç entity: &ccedil;   text: Latin small letter c with cedilla"
        "char: è entity: &egrave;   text: Latin small letter e with grave accent"
        "char: é entity: &eacute;   text: Latin small letter e with acute accent"
        "char: ê entity: &ecirc;    text: Latin small letter e with circumflex"
        "char: ë entity: &euml;     text: Latin small letter e with diaeresis"
        "char: ì entity: &igrave;   text: Latin small letter i with grave accent"
        "char: í entity: &iacute;   text: Latin small letter i with acute accent"
        "char: î entity: &icirc;    text: Latin small letter i with circumflex"
        "char: ï entity: &iuml;     text: Latin small letter i with diaeresis"
        "char: ð entity: &eth;      text: Latin small letter eth"
        "char: ñ entity: &ntilde;   text: Latin small letter n with tilde"
        "char: ò entity: &ograve;   text: Latin small letter o with grave accent"
        "char: ó entity: &oacute;   text: Latin small letter o with acute accent"
        "char: ô entity: &ocirc;    text: Latin small letter o with circumflex"
        "char: õ entity: &otilde;   text: Latin small letter o with tilde"
        "char: ö entity: &ouml;     text: Latin small letter o with diaeresis"
        "char: ÷ entity: &divide;   text: division sign (obelus)"
        "char: ø entity: &oslash;   text: Latin small letter o with stroke (Latin small letter o slash)"
        "char: ù entity: &ugrave;   text: Latin small letter u with grave accent"
        "char: ú entity: &uacute;   text: Latin small letter u with acute accent"
        "char: û entity: &ucirc;    text: Latin small letter u with circumflex"
        "char: ü entity: &uuml;     text: Latin small letter u with diaeresis"
        "char: ý entity: &yacute;   text: Latin small letter y with acute accent"
        "char: þ entity: &thorn;    text: Latin small letter thorn"
        "char: ÿ entity: &yuml;     text: Latin small letter y with diaeresis"
        "char: Πentity: &OElig;    text: Latin capital ligature oe[e]"
        "char: œ entity: &oelig;    text: Latin small ligature oe[e]"
        "char: Š entity: &Scaron;   text: Latin capital letter s with caron"
        "char: š entity: &scaron;   text: Latin small letter s with caron"
        "char: Ÿ entity: &Yuml;     text: Latin capital letter y with diaeresis"
        "char: ƒ entity: &fnof;     text: Latin small letter f with hook (function, florin)"
        "char: ˆ entity: &circ;     text: modifier letter circumflex accent"
        "char: ˜ entity: &tilde;    text: small tilde"
        "char: Α entity: &Alpha;    text: Greek capital letter Alpha"
        "char: Β entity: &Beta;     text: Greek capital letter Beta"
        "char: Γ entity: &Gamma;    text: Greek capital letter Gamma"
        "char: Δ entity: &Delta;    text: Greek capital letter Delta"
        "char: Ε entity: &Epsilon;  text: Greek capital letter Epsilon"
        "char: Ζ entity: &Zeta;     text: Greek capital letter Zeta"
        "char: Η entity: &Eta;      text: Greek capital letter Eta"
        "char: Θ entity: &Theta;    text: Greek capital letter Theta"
        "char: Ι entity: &Iota;     text: Greek capital letter Iota"
        "char: Κ entity: &Kappa;    text: Greek capital letter Kappa"
        "char: Λ entity: &Lambda;   text: Greek capital letter Lambda"
        "char: Μ entity: &Mu;       text: Greek capital letter Mu"
        "char: Ν entity: &Nu;       text: Greek capital letter Nu"
        "char: Ξ entity: &Xi;       text: Greek capital letter Xi"
        "char: Ο entity: &Omicron;  text: Greek capital letter Omicron"
        "char: Π entity: &Pi;       text: Greek capital letter Pi"
        "char: Ρ entity: &Rho;      text: Greek capital letter Rho"
        "char: Σ entity: &Sigma;    text: Greek capital letter Sigma"
        "char: Τ entity: &Tau;      text: Greek capital letter Tau"
        "char: Υ entity: &Upsilon;  text: Greek capital letter Upsilon"
        "char: Φ entity: &Phi;      text: Greek capital letter Phi"
        "char: Χ entity: &Chi;      text: Greek capital letter Chi"
        "char: Ψ entity: &Psi;      text: Greek capital letter Psi"
        "char: Ω entity: &Omega;    text: Greek capital letter Omega"
        "char: α entity: &alpha;    text: Greek small letter alpha"
        "char: β entity: &beta;     text: Greek small letter beta"
        "char: γ entity: &gamma;    text: Greek small letter gamma"
        "char: δ entity: &delta;    text: Greek small letter delta"
        "char: ε entity: &epsilon;  text: Greek small letter epsilon"
        "char: ζ entity: &zeta;     text: Greek small letter zeta"
        "char: η entity: &eta;      text: Greek small letter eta"
        "char: θ entity: &theta;    text: Greek small letter theta"
        "char: ι entity: &iota;     text: Greek small letter iota"
        "char: κ entity: &kappa;    text: Greek small letter kappa"
        "char: λ entity: &lambda;   text: Greek small letter lambda"
        "char: μ entity: &mu;       text: Greek small letter mu"
        "char: ν entity: &nu;       text: Greek small letter nu"
        "char: ξ entity: &xi;       text: Greek small letter xi"
        "char: ο entity: &omicron;  text: Greek small letter omicron"
        "char: π entity: &pi;       text: Greek small letter pi"
        "char: ρ entity: &rho;      text: Greek small letter rho"
        "char: ς entity: &sigmaf;   text: Greek small letter final sigma"
        "char: σ entity: &sigma;    text: Greek small letter sigma"
        "char: τ entity: &tau;      text: Greek small letter tau"
        "char: υ entity: &upsilon;  text: Greek small letter upsilon"
        "char: φ entity: &phi;      text: Greek small letter phi"
        "char: χ entity: &chi;      text: Greek small letter chi"
        "char: ψ entity: &psi;      text: Greek small letter psi"
        "char: ω entity: &omega;    text: Greek small letter omega"
        "char: ϑ entity: &thetasym; text: Greek theta symbol"
        "char: ϒ entity: &upsih;    text: Greek Upsilon with hook symbol"
        "char: ϖ entity: &piv;      text: Greek pi symbol"
        "char:   entity: &ensp;     text: en space[d]"
        "char:   entity: &emsp;     text: em space[d]"
        "char:   entity: &thinsp;   text: thin space[d]"
        "char:   entity: &zwnj;     text: zero-width non-joiner"
        "char:   entity: &zwj;      text: zero-width joiner"
        "char:   entity: &lrm;      text: left-to-right mark"
        "char:   entity: &rlm;      text: right-to-left mark"
        "char: – entity: &ndash;    text: en dash"
        "char: — entity: &mdash;    text: em dash"
        "char: ‘ entity: &lsquo;    text: left single quotation mark"
        "char: ’ entity: &rsquo;    text: right single quotation mark"
        "char: ‚ entity: &sbquo;    text: single low-9 quotation mark"
        "char: “ entity: &ldquo;    text: left double quotation mark"
        "char: ” entity: &rdquo;    text: right double quotation mark"
        "char: „ entity: &bdquo;    text: double low-9 quotation mark"
        "char: † entity: &dagger;   text: dagger, obelisk"
        "char: ‡ entity: &Dagger;   text: double dagger, double obelisk"
        "char: • entity: &bull;     text: bullet (black small circle)[f]"
        "char: … entity: &hellip;   text: horizontal ellipsis (three dot leader)"
        "char: ‰ entity: &permil;   text: per mille sign"
        "char: ′ entity: &prime;    text: prime (minutes, feet)"
        "char: ″ entity: &Prime;    text: double prime (seconds, inches)"
        "char: ‹ entity: &lsaquo;   text: single left-pointing angle quotation mark[g]"
        "char: › entity: &rsaquo;   text: single right-pointing angle quotation mark[g]"
        "char: ‾ entity: &oline;    text: overline (spacing overscore)"
        "char: ⁄ entity: &frasl;    text: fraction slash (solidus)"
        "char: € entity: &euro;     text: euro sign"
        "char: ℑ entity: &image;    text: black-letter capital I (imaginary part)"
        "char: ℘ entity: &weierp;   text: script capital P (power set, Weierstrass p)"
        "char: ℜ entity: &real;     text: black-letter capital R (real part symbol)"
        "char: ™ entity: &trade;    text: trademark symbol"
        "char: ℵ entity: &alefsym;  text: alef symbol (first transfinite cardinal)[h]"
        "char: ← entity: &larr;     text: leftwards arrow"
        "char: ↑ entity: &uarr;     text: upwards arrow"
        "char: → entity: &rarr;     text: rightwards arrow"
        "char: ↓ entity: &darr;     text: downwards arrow"
        "char: ↔ entity: &harr;     text: left right arrow"
        "char: ↵ entity: &crarr;    text: downwards arrow with corner leftwards (carriage return)"
        "char: ⇐ entity: &lArr;     text: leftwards double arrow[i]"
        "char: ⇑ entity: &uArr;     text: upwards double arrow"
        "char: ⇒ entity: &rArr;     text: rightwards double arrow[j]"
        "char: ⇓ entity: &dArr;     text: downwards double arrow"
        "char: ⇔ entity: &hArr;     text: left right double arrow"
        "char: ∀ entity: &forall;   text: for all"
        "char: ∂ entity: &part;     text: partial differential"
        "char: ∃ entity: &exist;    text: there exists"
        "char: ∅ entity: &empty;    text: empty set (null set); see also U+8960, ⌀"
        "char: ∇ entity: &nabla;    text: del or nabla (vector differential operator)"
        "char: ∈ entity: &isin;     text: element of"
        "char: ∉ entity: &notin;    text: not an element of"
        "char: ∋ entity: &ni;       text: contains as member"
        "char: ∏ entity: &prod;     text: n-ary product (product sign)[k]"
        "char: ∑ entity: &sum;      text: n-ary summation[l]"
        "char: − entity: &minus;    text: minus sign"
        "char: ∗ entity: &lowast;   text: asterisk operator"
        "char: √ entity: &radic;    text: square root (radical sign)"
        "char: ∝ entity: &prop;     text: proportional to"
        "char: ∞ entity: &infin;    text: infinity"
        "char: ∠ entity: &ang;      text: angle"
        "char: ∧ entity: &and;      text: logical and (wedge)"
        "char: ∨ entity: &or;       text: logical or (vee)"
        "char: ∩ entity: &cap;      text: intersection (cap)"
        "char: ∪ entity: &cup;      text: union (cup)"
        "char: ∫ entity: &int;      text: integral"
        "char: ∴ entity: &there4;   text: therefore sign"
        "char: ∼ entity: &sim;      text: tilde operator (varies with, similar to)[m]"
        "char: ≅ entity: &cong;     text: congruent to"
        "char: ≈ entity: &asymp;    text: almost equal to (asymptotic to)"
        "char: ≠ entity: &ne;       text: not equal to"
        "char: ≡ entity: &equiv;    text: identical to; sometimes used for 'equivalent to'"
        "char: ≤ entity: &le;       text: less-than or equal to"
        "char: ≥ entity: &ge;       text: greater-than or equal to"
        "char: ⊂ entity: &sub;      text: subset of"
        "char: ⊃ entity: &sup;      text: superset of[n]"
        "char: ⊄ entity: &nsub;     text: not a subset of"
        "char: ⊆ entity: &sube;     text: subset of or equal to"
        "char: ⊇ entity: &supe;     text: superset of or equal to"
        "char: ⊕ entity: &oplus;    text: circled plus (direct sum)"
        "char: ⊗ entity: &otimes;   text: circled times (vector product)"
        "char: ⊥ entity: &perp;     text: up tack (orthogonal to, perpendicular)[o]"
        "char: ⋅ entity: &sdot;     text: dot operator[p]"
        "char: ⌈ entity: &lceil;    text: left ceiling (APL upstile)"
        "char: ⌉ entity: &rceil;    text: right ceiling"
        "char: ⌊ entity: &lfloor;   text: left floor (APL downstile)"
        "char: ⌋ entity: &rfloor;   text: right floor"
        "char: 〈 entity: &lang;    text: left-pointing angle bracket (bra)[q]"
        "char: 〉 entity: &rang;    text: right-pointing angle bracket (ket)[r]"
        "char: ◊ entity: &loz;      text: lozenge"
        "char: ♠ entity: &spades;   text: black spade suit[f]"
        "char: ♣ entity: &clubs;    text: black club suit (shamrock)[f]"
        "char: ♥ entity: &hearts;   text: black heart suit (valentine)[f]"
        "char: ♦ entity: &diams;    text: black diamond suit[f]")
   "List of HTML entities with helpful text notes.

Scraped from Wikipedia at https://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references")

    (defun _html-entity-select ()
      "Select an html entry from the list."
      (interactive)
      (completing-read "HTML Entity: " _html-entity-list))

    (let ((entry (_html-entity-select)))
      (string-match "entity: \\(&.*?;\\)" entry)
      (insert (match-string 1 entry))))