JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="fes-category-checklist">

  <li id="download_category-156"><label class="selectit"><input value="156" type="checkbox" name="download_category[]" id="in-download_category-156"> cat a</label>
    <ul class="children">

      <li id="download_category-161"><label class="selectit"><input value="161" type="checkbox" name="download_category[]" id="in-download_category-161"> cat a-1</label></li>

      <li id="download_category-162"><label class="selectit"><input value="162" type="checkbox" name="download_category[]" id="in-download_category-162"> cat a-2</label></li>

      <li id="download_category-163"><label class="selectit"><input value="163" type="checkbox" name="download_category[]" id="in-download_category-163"> cat a-3</label></li>

      <li id="download_category-183"><label class="selectit"><input value="183" type="checkbox" name="download_category[]" id="in-download_category-183"> cat a-4</label></li>
    </ul>
  </li>

  <li id="download_category-160"><label class="selectit"><input value="160" type="checkbox" name="download_category[]" id="in-download_category-160"> cat b</label>
    <ul class="children">

      <li id="download_category-198"><label class="selectit"><input value="198" type="checkbox" name="download_category[]" id="in-download_category-198"> cat b-1</label></li>

      <li id="download_category-199"><label class="selectit"><input value="199" type="checkbox" name="download_category[]" id="in-download_category-199"> cat b-2</label></li>

      <li id="download_category-200"><label class="selectit"><input value="200" type="checkbox" name="download_category[]" id="in-download_category-200"> cat b-3</label></li>

      <li id="download_category-201"><label class="selectit"><input value="201" type="checkbox" name="download_category[]" id="in-download_category-201"> cat b-4</label></li>
    </ul>
  </li>

  <li id="download_category-155"><label class="selectit"><input value="155" type="checkbox" name="download_category[]"...

JavaScript

$('#in-download_category-156').click(function() {
  $(".children").toggle(this.checked);
});

$('#in-download_category-160').click(function() {
  $(".children").toggle(this.checked);
});

$('#in-download_category-155').click(function() {
  $(".children").toggle(this.checked);
});