How To Connect A Child Item In A Tree-structure Visualization With CSS

I want to create a list of items and sub items that are connected with lines. So far I have done this - As you can see, Sub Task 3 is not fully connected with its parent. How to

Solution 1:

I would do it differently like below:

.main {
  overflow: hidden;
}
ul {
  list-style: none;
  padding: 0;
  margin-left: 30px;
  margin-top: 10px;
}
.item {
  position: relative;
  line-height: 1.2em;
}
.item::before,
.item::after,
.item:last-child .sub-menu::before{
  content: '';
  background: #000;
  position: absolute;

}
.item::before {
  width: 10px;
  height: 1px;
  top: 0.5em;
  left: -10px;
}

.item::after {
  left: 20px;
  bottom: 0.6em;
  top: 1.2em;
  width: 1px;
}
/* the bekow will avoid the line to go down if there is no sub task (not transparent!)*/
.item:last-child > .sub-menu::before {
  top: calc(0.6em - 1px);
  width: 6px;
  bottom: 0;
  background: #fff;
  left: -12px;
  z-index: 1;
}

<ul class="main">
  <li class="item">Task 1</li>

  <li class="item">Task 2
    <ul class="sub-menu">
      <li class="item">Sub Task 1</li>

      <li class="item">Sub Task 2
        <ul class="sub-menu">
          <li class="item">Sub Task 1</li>
          <li class="item">Sub Task 2</li>
        </ul>
      </li>

      <li class="item">Sub Task 3
        <ul class="sub-menu">
          <li class="item">Sub Task 1</li>
          <li class="item">Sub Task 2
            <ul class="sub-menu">
              <li class="item">Sub Task 1</li>
              <li class="item">Sub Task 2</li>
            </ul>
          </li>
          <li class="item">Sub Task 3</li>
          <li class="item">Sub Task 4</li>
        </ul>
      </li>
    </ul>
  </li>

  <li class="item">Task 3</li>
</ul>