Verschachteln von Optgruppen in einer Dropdown-Liste / Auswahl

<select>
  <optgroup label="Level One">
    <option> A.1 </option>
    <optgroup label="Level Two">
      <option> A.B.1 </option>
    </optgroup>
    <option> A.2 </option>
  </optgroup>
</select>

<select>
  <optgroup label="Level One">
    <option> A.1 </option>
    <optgroup label="&nbsp;&nbsp;&nbsp;&nbsp;Level Two">
      <option>&nbsp;&nbsp;&nbsp;&nbsp; A.B.1 </option>
    </optgroup>
    <option> A.2 </option>
  </optgroup>
  <option> A </option>
</select>

<select>
  <optgroup label="Level One"></optgroup>
  <option style="padding-left:15px"> A.1 </option>
  <optgroup label="Level Two" style="padding-left:15px"></optgroup>
  <option style="padding-left:30px"> A.B.1 </option>
  <option style="padding-left:15px"> A.2 </option>
  <option> A </option>
</select>

<select>
 <optgroup label="Level One">
  <option> A.1 </option>
  <optgroup label="&nbsp;&nbsp;&nbsp;&nbsp;Level Two">
   <option>&nbsp;&nbsp;&nbsp;&nbsp; A.B.1 </option>
  </optgroup>
  <option> A.2 </option>
 </optgroup>
</select>

<style>
  .NestedSelect{display: inline-block; height: 100px; border: 1px Black solid; overflow-y: scroll;}
  .NestedSelect label{display: block; cursor: pointer;}
  .NestedSelect label:hover{background-color: #0092ff; color: White;}
  .NestedSelect input[type="radio"]{display: none;}
  .NestedSelect input[type="radio"] + span{display: block; padding-left: 0px; padding-right: 5px;}
  .NestedSelect input[type="radio"]:checked + span{background-color: Black; color: White;}
  .NestedSelect div{margin-left: 15px; border-left: 1px Black solid;}
  .NestedSelect label > span:before{content: '- ';}
</style>

<div class="NestedSelect">
  <label><input type="radio" name="MySelectInputName"><span>Fruit</span></label>
  <div>
    <label><input type="radio" name="MySelectInputName"><span>Apple</span></label>
    <label><input type="radio" name="MySelectInputName"><span>Banana</span></label>
    <label><input type="radio" name="MySelectInputName"><span>Orange</span></label>
  </div>

  <label><input type="radio" name="MySelectInputName"><span>Drink</span></label>
  <div>
    <label><input type="radio" name="MySelectInputName"><span>Water</span></label>

    <label><input type="radio" name="MySelectInputName"><span>Soft</span></label>
    <div>
      <label><input type="radio" name="MySelectInputName"><span>Cola</span></label>
      <label><input type="radio" name="MySelectInputName"><span>Soda</span></label>
      <label><input type="radio" name="MySelectInputName"><span>Lemonade</span></label>
    </div>

    <label><input type="radio" name="MySelectInputName"><span>Hard</span></label>
    <div>
      <label><input type="radio" name="MySelectInputName"><span>Bear</span></label>
      <label><input type="radio" name="MySelectInputName"><span>Whisky</span></label>
      <label><input type="radio" name="MySelectInputName"><span>Vodka</span></label>
      <label><input type="radio" name="MySelectInputName"><span>Gin</span></label>
    </div>
  </div>
</div>

<ul>
  <li>
	<input type="radio" name="location" value="0" id="loc_0" />
	<label for="loc_0">United States</label>
	<ul>
	  <li>
		Northeast
        <ul>
	      <li>
			<input type="radio" name="location" value="1" id="loc_1" />
			<label for="loc_1">New Hampshire</label>
		  </li>
          <li>
			<input type="radio" name="location" value="2" id="loc_2" />
			<label for="loc_2">Vermont</label>
		  </li>
          <li>
			 <input type="radio" name="location" value="3" id="loc_3" />
			 <label for="loc_3">Maine</label>
		  </li>
		 </ul>
	   </li>
       <li>
		   Southeast
           <ul>
			 <li>
				<input type="radio" name="location" value="4" id="loc_4" />
				<label for="loc_4">Georgia</label>
			 </li>
             <li>
				<input type="radio" name="location" value="5" id="loc_5" />
				<label for="loc_5">Alabama</label>
			 </li>
		   </ul>
		</li>
	  </ul>
    </li>
    <li>
	   <input type="radio" name="location" value="6" id="loc_6" />
	   <label for="loc_6">Canada</label>
       <ul>
		  <li>
			 <input type="radio" name="location" value="7" id="loc_7" />
			 <label for="loc_7">Ontario</label>
		  </li>
          <li>
			  <input type="radio" name="location" value="8" id="loc_8" />
		      <label for="loc_8">Quebec</label>
		  </li>
          <li>
			   <input type="radio" name="location" value="9" id="loc_9" />
			   <label for="loc_9">Manitoba</label>
		  </li>
		</ul>
	 </li>
  </ul>

function on_change_select(e) {
  alert(e.value, e.title, e.option, e.select);
}

$(document).ready(() => {
  // NESTED SELECT

  $(document).on('click', '.nested-cell', function() {
    $(this).next('div').toggle('medium');
  });

  $(document).on('change', 'input[name="nested-select-hidden-radio"]', function() {
    const parent = $(this).closest(".nested-select");
    const value = $(this).attr('value');
    const title = $(this).attr('title');
    const executer = parent.attr('executer');
    if (executer) {
      const event = new Object();
      event.value = value;
      event.title = title;
      event.option = $(this);
      event.select = parent;
      window[executer].apply(null, [event]);
    }
    parent.attr('value', value);
    parent.parent().slideToggle();
    const button = parent.parent().prev();
    button.toggleClass('active');
    button.addClass('selected');
    button.children('.nested-select-title').html(title);
  });

  $(document).on('click', '.nested-select-button', function() {
    const button = $(this);
    let select = button.parent().children('.nested-select-wrapper');

    if (!button.hasClass('active')) {
      select = select.detach();
      if (button.height() + button.offset().top + $(window).height() * 0.4 > $(window).height()) {
        select.insertBefore(button);
        select.css('margin-top', '-44vh');
        select.css('top', '0');
      } else {
        select.insertAfter(button);
        select.css('margin-top', '');
        select.css('top', '40px');
      }
    }
    select.slideToggle();
    button.toggleClass('active');
  });
});

.container {
  width: 200px;
  position: relative;
  top: 0;
  left: 0;
  right: 0;
  height: auto;
}

.nested-select-box {
  font-family: Arial, Helvetica, sans-serif;
  display: block;
  position: relative;
  width: 100%;
  height: fit-content;
  cursor: pointer;
  color: #2196f3;
  height: 40px;
  font-size: small;
  /* z-index: 2000; */
}

.nested-select-box .nested-select-button {
  border: 1px solid #2196f3;
  position: absolute;
  width: calc(100% - 20px);
  padding: 0 10px;
  min-height: 40px;
  word-wrap: break-word;
  margin: 0 auto;
  overflow: hidden;
}

.nested-select-box.danger .nested-select-button {
  border: 1px solid rgba(250, 33, 33, 0.678);
}

.nested-select-box .nested-select-button .nested-select-title {
  padding-right: 25px;
  padding-left: 25px;
  width: calc(100% - 50px);
  margin: auto;
  height: fit-content;
  text-align: center;
  vertical-align: middle;
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
}

.nested-select-box .nested-select-button.selected .nested-select-title {
  bottom: unset;
  top: 5px;
}

.nested-select-box .nested-select-button .nested-select-title-icon {
  position: absolute;
  height: 20px;
  width: 20px;
  top: 10px;
  bottom: 10px;
  right: 7px;
  transition: all 0.5s ease 0s;
}

.nested-select-box .nested-select-button.active .nested-select-title-icon {
  -moz-transform: scale(-1, -1);
  -o-transform: scale(-1, -1);
  -webkit-transform: scale(-1, -1);
  transform: scale(-1, -1);
}

.nested-select-box .nested-select-button .nested-select-title-icon::before,
.nested-select-box .nested-select-button .nested-select-title-icon::after {
  content: "";
  background-color: #2196f3;
  position: absolute;
  width: 70%;
  height: 2px;
  transition: all 0.5s ease 0s;
  top: 9px;
}

.nested-select-box .nested-select-button .nested-select-title-icon::before {
  transform: rotate(45deg);
  left: -1.6px;
}

.nested-select-box .nested-select-button .nested-select-title-icon::after {
  transform: rotate(-45deg);
  left: 7px;
}

.nested-select-box .nested-select-wrapper {
  width: 100%;
  top: 40px;
  position: relative;
  border: 1px solid #2196f3;
  background: #ffffff;
  z-index: 2005;
  opacity: 1;
}

.nested-select {
  font-family: Arial, Helvetica, sans-serif;
  display: inline-block;
  overflow-y: scroll;
  max-height: 40vh;
  width: calc(100% - 10px);
  padding: 5px;
  -ms-overflow-style: none;
  scrollbar-width: none;
}

.nested-select::-webkit-scrollbar {
  display: none;
}

.nested-select a,
.nested-select span {
  padding: 0 5px;
  border-radius: 3px;
  cursor: pointer;
  text-align: start;
}

.nested-select a:hover {
  background-color: #62b2f3;
  color: #ffffff;
}

.nested-select span:hover {
  background-color: #c4c4c4;
  color: #ffffff;
}

.nested-select input[type="radio"] {
  display: none;
}

.nested-select input[type="radio"]+span {
  display: block;
}

.nested-select input[type="radio"]:checked+span {
  background-color: #2196f3;
  color: #ffffff;
}

.nested-select div {
  margin-left: 15px;
}

.nested-select label>span:before,
.nested-select a:before {
  content: "\2022";
  margin-right: 5px;
}

.nested-select a {
  display: block;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="container">
  <div class="nested-select-box w-100">
    <div class="nested-select-button">
      <p class="nested-select-title">
        Account
      </p>
      <span class="nested-select-title-icon"></span>
    </div>
    <div class="nested-select-wrapper" style="display: none;">
      <div class="nested-select" executer="on_change_select">

        <label>
        <input title="Accounting and legal services" value="1565142000000891539" type="radio" name="nested-select-hidden-radio">
        <span>Accounting and legal services</span>
      </label>



        <label>
        <input title="Advertising agencies" value="1565142000000891341" type="radio" name="nested-select-hidden-radio">
        <span>Advertising agencies</span>
      </label>



        <a class="nested-cell">Advertising And Marketing</a>
        <div>



          <label>
          <input title="Advertising agencies" value="1565142000000891341" type="radio" name="nested-select-hidden-radio">
          <span>Advertising agencies</span>
        </label>



          <a class="nested-cell">Adwords - traffic</a>
          <div>



            <label>
            <input title="Adwords - traffic: Charters and general search" value="1565142000003929177" type="radio" name="nested-select-hidden-radio">
            <span>Adwords - traffic: Charters and general search</span>
          </label>



            <label>
            <input title="Adwords - traffic: Distance course" value="1565142000007821291" type="radio" name="nested-select-hidden-radio">
            <span>Adwords - traffic: Distance course</span>
          </label>



            <label>
            <input title="Adwords - traffic: Events" value="1565142000003929189" type="radio" name="nested-select-hidden-radio">
            <span>Adwords - traffic: Events</span>
          </label>



            <label>
            <input title="Adwords - traffic: Practices" value="1565142000003929165" type="radio" name="nested-select-hidden-radio">
            <span>Adwords - traffic: Practices</span>
          </label>



            <label>
            <input title="Adwords - traffic: Sailing tours" value="1565142000003929183" type="radio" name="nested-select-hidden-radio">
            <span>Adwords - traffic: Sailing tours</span>
          </label>



            <label>
            <input title="Adwords - traffic: Theoretical courses" value="1565142000003929171" type="radio" name="nested-select-hidden-radio">
            <span>Adwords - traffic: Theoretical courses</span>
          </label>



          </div>



          <label>
          <input title="Branded products" value="1565142000000891533" type="radio" name="nested-select-hidden-radio">
          <span>Branded products</span>
        </label>



          <label>
          <input title="Business cards" value="1565142000005438323" type="radio" name="nested-select-hidden-radio">
          <span>Business cards</span>
        </label>



          <a class="nested-cell">Facebook, Instagram - traffic</a>
          <div>



            <label>
            <input title="Facebook, Instagram - traffic: Charters and general search" value="1565142000003929145" type="radio" name="nested-select-hidden-radio">
            <span>Facebook, Instagram - traffic: Charters and general search</span>
          </label>



            <label>
            <input title="Facebook, Instagram - traffic: Distance course" value="1565142000007821285" type="radio" name="nested-select-hidden-radio">
            <span>Facebook, Instagram - traffic: Distance course</span>
          </label>



            <label>
            <input title="Facebook, Instagram - traffic: Events" value="1565142000003929157" type="radio" name="nested-select-hidden-radio">
            <span>Facebook, Instagram - traffic: Events</span>
          </label>



            <label>
            <input title="Facebook, Instagram - traffic: Practices" value="1565142000003929133" type="radio" name="nested-select-hidden-radio">
            <span>Facebook, Instagram - traffic: Practices</span>
          </label>



            <label>
            <input title="Facebook, Instagram - traffic: Sailing tours" value="1565142000003929151" type="radio" name="nested-select-hidden-radio">
            <span>Facebook, Instagram - traffic: Sailing tours</span>
          </label>



            <label>
            <input title="Facebook, Instagram - traffic: Theoretical courses" value="1565142000003929139" type="radio" name="nested-select-hidden-radio">
            <span>Facebook, Instagram - traffic: Theoretical courses</span>
          </label>



          </div>



          <label>
          <input title="Offline Advertising (posters, banners, partnerships)" value="1565142000000891377" type="radio" name="nested-select-hidden-radio">
          <span>Offline Advertising (posters, banners, partnerships)</span>
        </label>



          <label>
          <input title="Photos, video etc." value="1565142000000891371" type="radio" name="nested-select-hidden-radio">
          <span>Photos, video etc.</span>
        </label>



          <label>
          <input title="Prize fund" value="1565142000001404931" type="radio" name="nested-select-hidden-radio">
          <span>Prize fund</span>
        </label>



          <label>
          <input title="SEO" value="1565142000000891365" type="radio" name="nested-select-hidden-radio">
          <span>SEO</span>
        </label>



          <label>
          <input title="SMM Content creation (texts, copywriting)" value="1565142000000891389" type="radio" name="nested-select-hidden-radio">
          <span>SMM Content creation (texts, copywriting)</span>
        </label>



          <a class="nested-cell">YouTube</a>
          <div>



            <label>
            <input title="YouTube: travel expenses" value="1565142000008100163" type="radio" name="nested-select-hidden-radio">
            <span>YouTube: travel expenses</span>
          </label>



            <label>
            <input title="Youtube: video editing" value="1565142000008100157" type="radio" name="nested-select-hidden-radio">
            <span>Youtube: video editing</span>
          </label>



          </div>



        </div>

      </div>
    </div>
  </div>
</div>