JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="list_1">
  <li class="list_1_items">
    <label for="check">Элемент 1</label>
    <input type="checkbox" name="check" id="check">
    <ul class="list_2">
      <li class="list_2_items"><a href="">Элемент 1_1</a></li>
		  <li class="list_2_items"><a href="">Элемент 1_2</a></li>
    </ul>
  </li> 
 </ul>

CSS

.list_2 {
  	display: none;
}


 input[type=checkbox]:checked + .list_2 {
  	display: block
}