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.

Tran Ngoc Tuan Anh

eLightUp

Admin Taxonomy Filter helps you to filter posts or custom post types in the admin area (the post list table) by custom taxonomies. It’s similar to filter posts by categories, which is supported by default.
The plugin supports filter by multiple taxonomies and has settings to let you choose which taxonomies are filterable.
The plugin is open source and hosted on <a href="https://github.com/rilwis/admin-taxonomy-filter/" rel="nofollow ugc">Github</a>. If you have any problem or feedback, please open an issue.
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Admin Taxonomy Filter

Works fine for custom post types and help in navigation in the posts backend



Works fine for custom post types

Filter posts or custom post types in the admin area by custom taxonomies.

Taxonomy Admin Search vs Admin Taxonomy Filter