Ordered lists, flat or nested, multiple formats ordered lists; Fetch from https://github.com/sethyuan/logseq-plugin-ol/blob/master/src/index.js#L9-L226 ; Add `@Import` in custom.css on Logseq;

logseq-plugin-ol.css

a[data-ref|='.ol'],
a[data-ref|='.ul'] {
  display: none !important;
}
.cp__all_pages_table :is(a[data-ref|='.ol'], a[data-ref|='.ul']) {
  display: unset !important;
}

.ls-block[data-refs-self*='".ol'] .block-children {
  counter-reset: kef-ol;
}
.ls-block[data-refs-self*='".ol-2'] .block-children {
  counter-reset: kef-ol 1;
}
.ls-block[data-refs-self*='".ol-3'] .block-children {
  counter-reset: kef-ol 2;
}
.ls-block[data-refs-self*='".ol-4'] .block-children {
  counter-reset: kef-ol 3;
}
.ls-block[data-refs-self*='".ol-5'] .block-children {
  counter-reset: kef-ol 4;
}
.ls-block[data-refs-self*='".ol-6'] .block-children {
  counter-reset: kef-ol 5;
}
.ls-block[data-refs-self*='".ol-7'] .block-children {
  counter-reset: kef-ol 6;
}
.ls-block[data-refs-self*='".ol-8'] .block-children {
  counter-reset: kef-ol 7;
}
.ls-block[data-refs-self*='".ol-9'] .block-children {
  counter-reset: kef-ol 8;
}
.ls-block[data-refs-self*='".ol-10'] .block-children {
  counter-reset: kef-ol 9;
}

.ls-block[data-refs-self*='".ol-nested'] .block-children {
  counter-reset: kef-ol-nested;
}
.ls-block[data-refs-self*='".ol-nested-s2'] > .block-children-container > .block-children {
  counter-reset: kef-ol 1 kef-ol-nested 1;
}
.ls-block[data-refs-self*='".ol-nested-s3'] > .block-children-container > .block-children {
  counter-reset: kef-ol 2 kef-ol-nested 2;
}
.ls-block[data-refs-self*='".ol-nested-s4'] > .block-children-container > .block-children {
  counter-reset: kef-ol 3 kef-ol-nested 3;
}
.ls-block[data-refs-self*='".ol-nested-s5'] > .block-children-container > .block-children {
  counter-reset: kef-ol 4 kef-ol-nested 4;
}
.ls-block[data-refs-self*='".ol-nested-s6'] > .block-children-container > .block-children {
  counter-reset: kef-ol 5 kef-ol-nested 5;
}
.ls-block[data-refs-self*='".ol-nested-s7'] > .block-children-container > .block-children {
  counter-reset: kef-ol 6 kef-ol-nested 6;
}
.ls-block[data-refs-self*='".ol-nested-s8'] > .block-children-container > .block-children {
  counter-reset: kef-ol 7 kef-ol-nested 7;
}
.ls-block[data-refs-self*='".ol-nested-s9'] > .block-children-container > .block-children {
  counter-reset: kef-ol 8 kef-ol-nested 8;
}
.ls-block[data-refs-self*='".ol-nested-s10'] > .block-children-container > .block-children {
  counter-reset: kef-ol 9 kef-ol-nested 9;
}

.ls-block[data-refs-self*='".ol'] > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container {
  width: auto !important;
  height: auto !important;
  background-color: transparent !important;
  z-index: 1 !important;
}
.ls-block[data-refs-self*='".ol'] .ls-block > div > div > a + a > .bullet-container::before {
  display: none;
}
.ls-block[data-refs-self*='".ol'] > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container::before {
  display: block;
  counter-increment: kef-ol;
  content: counter(kef-ol) ". ";
  font-family: "Tahoma", sans-serif;
  font-size: 0.85em;
  min-width: max-content;
}
.ls-block[data-refs-self*='".ol'] > .block-children-container > .block-children > .ls-block > div:has(:is(.flex-1 > h1, .editor-inner .h1)) > div > a + a > .bullet-container::before {
  font-size: calc(2em * 0.85);
}
.ls-block[data-refs-self*='".ol'] > .block-children-container > .block-children > .ls-block > div:has(:is(.flex-1 > h2, .editor-inner .h2)) > div > a + a > .bullet-container::before {
  font-size: calc(1.5em * 0.85);
}
.ls-block[data-refs-self*='".ol'] > .block-children-container > .block-children > .ls-block > div:has(:is(.flex-1 > h3, .editor-inner .h3)) > div > a + a > .bullet-container::before {
  font-size: calc(1.2em * 0.85);
}
.ls-block[data-refs-self*='".ol'] > .block-children-container > .block-children > .ls-block > div:has(:is(.flex-1 > h4, .editor-inner .h4)) > div > a + a > .bullet-container::before {
  font-size: calc(1em * 0.85);
}
.ls-block[data-refs-self*='".ol'] > .block-children-container > .block-children > .ls-block > div:has(:is(.flex-1 > h5, .editor-inner .h5)) > div > a + a > .bullet-container::before {
  font-size: calc(0.83em * 0.85);
}
.ls-block[data-refs-self*='".ol'] > .block-children-container > .block-children > .ls-block > div:has(:is(.flex-1 > h6, .editor-inner .h6)) > div > a + a > .bullet-container::before {
  font-size: calc(0.75em * 0.85);
}
.ls-block[data-refs-self*='".ol'] .bullet-container > .bullet {
  display: block;
}
.ls-block[data-refs-self*='".ol'] > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container > .bullet {
  display: none;
}

.ls-block[data-refs-self*='".ol-nested'] > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container::before {
  counter-increment: kef-ol-nested;
  content: counters(kef-ol-nested, ".") ". ";
}
.ls-block[data-refs-self*='".ol-nested'] .ls-block > div > div > a + a > .bullet-container {
  width: auto !important;
  height: auto !important;
  background-color: transparent !important;
  z-index: 1 !important;
}
.ls-block[data-refs-self*='".ol-nested'] .ls-block > div > div > a + a > .bullet-container::before {
  display: block;
  counter-increment: kef-ol-nested;
  content: counters(kef-ol-nested, ".") ". ";
  font-family: "Tahoma", sans-serif;
  font-size: 0.85em;
  min-width: max-content;
}
.ls-block[data-refs-self*='".ol-nested'] .ls-block > div:has(:is(.flex-1 > h1, .editor-inner .h1)) > div > a + a > .bullet-container::before {
  font-size: calc(2em * 0.85);
}
.ls-block[data-refs-self*='".ol-nested'] .ls-block > div:has(:is(.flex-1 > h2, .editor-inner .h2)) > div > a + a > .bullet-container::before {
  font-size: calc(1.5em * 0.85);
}
.ls-block[data-refs-self*='".ol-nested'] .ls-block > div:has(:is(.flex-1 > h3, .editor-inner .h3)) > div > a + a > .bullet-container::before {
  font-size: calc(1.2em * 0.85);
}
.ls-block[data-refs-self*='".ol-nested'] .ls-block > div:has(:is(.flex-1 > h4, .editor-inner .h4)) > div > a + a > .bullet-container::before {
  font-size: calc(1em * 0.85);
}
.ls-block[data-refs-self*='".ol-nested'] .ls-block > div:has(:is(.flex-1 > h5, .editor-inner .h5)) > div > a + a > .bullet-container::before {
  font-size: calc(0.83em * 0.85);
}
.ls-block[data-refs-self*='".ol-nested'] .ls-block > div:has(:is(.flex-1 > h6, .editor-inner .h6)) > div > a + a > .bullet-container::before {
  font-size: calc(0.75em * 0.85);
}
.ls-block[data-refs-self*='".ol-nested'] .bullet-container > .bullet {
  display: none;
}
.ls-block[data-refs-self*='".ol-nested'] > div > div > a + a > .bullet-container > .bullet {
  display: block;
}

.ls-block[data-refs-self*='".ol'] .ls-block[data-refs-self*='".ul'] > div > div > a + a > .bullet-container > .bullet,
.ls-block[data-refs-self*='".ol-nested-2'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container > .bullet,
.ls-block[data-refs-self*='".ol-nested-3'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container > .bullet,
.ls-block[data-refs-self*='".ol-nested-right-paren-2'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container > .bullet,
.ls-block[data-refs-self*='".ol-nested-right-paren-3'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container > .bullet {
  display: none;
}
.ls-block[data-refs-self*='".ol'] .ls-block[data-refs-self*='".ul'] .ls-block > div > div > a + a:hover > .bullet-container,
.ls-block[data-refs-self*='".ol-nested-2'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .ls-block > div > div > a + a:hover > .bullet-container,
.ls-block[data-refs-self*='".ol-nested-3'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .ls-block > div > div > a + a:hover > .bullet-container,
.ls-block[data-refs-self*='".ol-nested-right-paren-2'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .ls-block > div > div > a + a:hover > .bullet-container,
.ls-block[data-refs-self*='".ol-nested-right-paren-3'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .ls-block > div > div > a + a:hover > .bullet-container {
  background-color: var(--ls-block-bullet-border-color, #ced9e0) !important;
}
.ls-block[data-refs-self*='".ol'] .ls-block[data-refs-self*='".ul'] .ls-block > div > div > a + a > .bullet-container,
.ls-block[data-refs-self*='".ol-nested-2'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .ls-block > div > div > a + a > .bullet-container,
.ls-block[data-refs-self*='".ol-nested-3'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .ls-block > div > div > a + a > .bullet-container,
.ls-block[data-refs-self*='".ol-nested-right-paren-2'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .ls-block > div > div > a + a > .bullet-container,
.ls-block[data-refs-self*='".ol-nested-right-paren-3'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .ls-block > div > div > a + a > .bullet-container {
  width: 16px !important;
  height: 16px !important;
}
.ls-block[data-refs-self*='".ol'] .ls-block[data-refs-self*='".ul'] .ls-block > div > div > a + a > .bullet-container::before,
.ls-block[data-refs-self*='".ol-nested-2'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .ls-block > div > div > a + a > .bullet-container::before,
.ls-block[data-refs-self*='".ol-nested-3'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .ls-block > div > div > a + a > .bullet-container::before,
.ls-block[data-refs-self*='".ol-nested-right-paren-2'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .ls-block > div > div > a + a > .bullet-container::before,
.ls-block[data-refs-self*='".ol-nested-right-paren-3'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .ls-block > div > div > a + a > .bullet-container::before {
  display: none;
}
.ls-block[data-refs-self*='".ol'] .ls-block[data-refs-self*='".ul'] .bullet-container > .bullet,
.ls-block[data-refs-self*='".ol-nested-2'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .bullet-container > .bullet,
.ls-block[data-refs-self*='".ol-nested-3'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .bullet-container > .bullet,
.ls-block[data-refs-self*='".ol-nested-right-paren-2'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .bullet-container > .bullet,
.ls-block[data-refs-self*='".ol-nested-right-paren-3'] > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block > .block-children-container > .block-children > .ls-block .bullet-container > .bullet {
  display: flex;
}

.ls-block[data-refs-self*='".ol-paren'] > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container::before {
  content: "(" counter(kef-ol) ") ";
}
.ls-block[data-refs-self*='".ol-right-paren'] > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container::before {
  content: counter(kef-ol) ") ";
}
.ls-block[data-refs-self*='".ol-dun'] > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container::before {
  content: counter(kef-ol) "、";
}
.ls-block[data-refs-self*='".ol-circle'] > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container::before {
  content: counter(kef-ol);
  border-radius: 50%;
  border: 1px solid var(--ls-icon-color);
  width: 21px;
  height: 21px;
  text-align: center;
}
.ls-block[data-refs-self*='".ol-nested-right-paren'] > .block-children-container > .block-children > .ls-block > div > div > a + a > .bullet-container::before,
.ls-block[data-refs-self*='".ol-nested-right-paren'] .ls-block > div > div > a + a > .bullet-container::before {
  content: counters(kef-ol-nested, ".") ") ";
}

.ls-block[data-refs-self*='".ol'] .ls-block[haschild=true] > div > .block-content-wrapper::before {
  display: none;
}

Usage

@import url('https://gist.githubusercontent.com/bGZo/f81fa3bff567aaf9191afafbab6873d8/raw/6ae288bf1c5393addd6ae6e1606335e7a79c9bc6/logseq-plugin-ol.css');