Triweb Digital

This plugin injects a small search box at the top of taxonomy metaboxes (the checkbox lists) on the post edit screen. It only appears for taxonomies that have more than 5 terms to avoid clutter.
Search queries are performed via AJAX and the checklist is filtered client-side for a quick, responsive experience.

Taxonomy Admin Search

Adds an AJAX-powered search box to taxonomy metaboxes on the post edit screen when a taxonomy has more than 5 terms.

ImportWP

JC Submenu plugin allows you to automatically populate your navigation menus with custom post_types, taxonomies, or child pages. An easy to use plugin created to be a lightweight menu extension.
Also output a selected section of your dynamic menu through our advanced submenu widget.

JC Submenu

JC Submenu plugin allows you to automatically populate your navigation menus with custom post_types, taxonomies, or child pages.

Taxonomy Admin Search vs JC Submenu