nos3b3ar

This plugin is very useful if you have a lot of categories (or custom taxonomies) in more then one level. 
It helps to see the only the first level categories at first. You can open the submenus by click on the +buttons
Features: 
* Supports Gutenberg-Editor and Classic-Editor 
* Submenus are collapsed-in by default, except they have selected sub-items 
* The number of sub-items are displayed 
* Toggle (open/close) the submenus by + / – buttons 
* The font is bold if there are sub-items 
* It works with any custom taxonomy too
Notes: 
It’s very lightweight plugin. A simple solution by adding few lines of CSS an JS to the admin-area. less code, simple work. 😉
You found a bug or have any questions or wishes? Please let me comment there OR submit bugs and patches to https://github.com/nos3b3ar/admin-category-tree

Admin Category Tree

Changes the classic Admin-Category-View to an collapsed Tree-View with +/- buttons. (for all Post-Types, also…

aoulmderat

If you need to add more css and customization options to the Default WordPress Category Widget this plugin is for you. 
Using this plugin you can display your sidebar categories in a tree-view in just one click.
<h4>Features</h4>
<ul>
<li>The selection state is preserved (the parent category remain open)</li>
<li>Fully customized and easy to use</li>
<li>Display as dropdown or tree-view</li>
<li>Dynamically create your website tree for all posts & categories</li>
<li>Ability to hide/show count</li>
<li>Ability to hide/show child</li>
<li>When a child is selected The parent category is also selected</li>
</ul>

Display Categories Tree

for performance the css is loaded only when needed

Minimum style and js

This plugin is a widget to customize and add more css options to the Default Wordpress Category Widget. This plugin requires fontawesome in your theme …

Admin Category Tree vs Display Categories Tree