glyph_range.tex

\documentclass[a4paper]{article}
\usepackage{fontspec,multicol}
\usepackage[margin=2cm]{geometry}
\begin{document}

\ExplSyntaxOn
\DeclareDocumentCommand \fontrange { m m m +m }
 {
  \group_begin:
  \cs_set:Npn \__typeset:nnn ##1 ##2 ##3 {#4}
  \fontspec{#1}
  \int_step_inline:nnnn {#2} {1} {#3}
   {
    \iffontchar\font ##1\relax
      \__typeset:nnn {##1} { \int_to_Hex:n {##1} } { \char ##1 \relax }
    \fi
   }
  \group_end:
 }
\ExplSyntaxOff

\begin{multicols}{5}
\fontrange{xits-math.otf}{1}{"FFFFF}
  { \texttt{\small U+#2}:\quad #3\par}
  % #1 = glyph slot, decimal
  % #2 = glyph slot, hex
  % #3 = char
\end{multicols}

\end{document}