atillaordog

The search fields simply filter the lists in their current box.
Use the settings page to manage the location of search fields.
Simple as the sun, using easy JS.
Especially useful when there are a lot of categories, like in case of a shop.
It needs jQuery to run ! 
Trims beginning and ending spaces ! 
Works with the classic editor of WordPress 5, the new editor has this functionality included.

WP Admin Category Search

The plugin works flawlessly and is very simple.

Works fine and solved my problem

This plugin adds search functionality to category-like taxonomies and dropdowns like author on add / edit post / page admin pages.

FolioVision

This is a fix of Top Level Category plugin for WordPress 3.1. and further versions. It’s purpose is to provide the same behavior as the original plugin, but in new WordPress versions.
The Top Level Categories plugin allows you to remove the prefix before the URL to your category page. For example, instead of http://foliovision.com/category/work, you can use http://foliovision.com/work for the address of “work” category. WordPress doesn’t allow you to have a blank prefix for categories (they insert <code>category/</code> before the name), this plugin works around that restriction.
This plugin works also if you have a permalink structure like %postname% or %category%/%postname% — this wasn’t possible in the original version. However, this feature might not work properly for child categories at this point. Test carefully!
<a href="http://foliovision.com/support/fv-top-level-categories/" rel="nofollow ugc">Support</a>
<h3>Known Issues / Bugs</h3>
<ol>
<li>Issue with paging and feed URLs when using <code>%postname</code> or <code>%category%/%postname%</code> permalink structure should be fixed.</li>
</ol>
<h3>Uninstall</h3>
<ol>
<li>Deactivate the plugin</li>
<li>That’s it! 🙂</li>
</ol>

FV Top Level Categories

This is a fix of Top Level Categories plugin for Wordpress 3.1. and above.

WP Admin Category Search vs FV Top Level Categories