Tree diagram

<div class="tree-diagram">
<ul>
<li>
<!-- Content -->
...
<!-- Sub items -->
<ul>
<li>
<!-- Content -->
...
<!-- Sub items -->
<ul>
<li>...</li>
<li>...</li>
...
</ul>
</li>
<li>...</li>
...
</ul>
</li>
<!-- Repeat other items -->
...
</ul>
</div>
.tree-diagram ul {
display: flex;
position: relative;
/* Reset */
list-style-type: none;
margin: 0;
padding: 1rem 0.5rem 0rem 0.5rem;
}
.tree-diagram ul ul::before {
border-right: 1px solid rgba(0, 0, 0, 0.3);
content: '';
/* Position */
position: absolute;
top: 0;
right: 50%;
/* Size */
height: 1rem;
width: 50%;
}
.tree-diagram li {
padding: 1rem 0.5rem 0rem 0.5rem;
position: relative;
/* Center the content */
align-items: center;
display: flex;
flex-direction: column;
}
.tree-diagram li::before {
border-right: 1px solid rgba(0, 0, 0, 0.3);
border-top: 1px solid rgba(0, 0, 0, 0.3);
content: '';
/* Position */
position: absolute;
top: 0;
right: 50%;
/* Size */
height: 1rem;
width: 50%;
}
.tree-diagram li::after {
border-top: 1px solid rgba(0, 0, 0, 0.3);
content: '';
/* Position */
position: absolute;
top: 0;
right: 0;
/* Size */
width: 50%;
}
.tree-diagram li:first-child::before,
.tree-diagram li:last-child::after {
/* Remove the top of border from the first and last items */
border-top: none;
}
/* Add a root item if you want */
li.tree-diagram__root::before {
border-right: none;
}

See also

Folder structure