scribu

On the post editing screen, after saving a post, you will notice that the checked categories are displayed on top, breaking the category hierarchy. This plugin removes that “feature”.
Additionally, it automatically scrolls to the first checked category.
Works with custom taxonomies too.
Links: <a href="http://scribu.net/wordpress/category-checklist-tree" rel="nofollow ugc">Plugin News</a> | <a href="http://scribu.net" rel="nofollow ugc">Author’s Site</a>

Category Checklist Tree

Simple and without configuration, it's just does what it says it does.



Works as expected

Really, I just can't understand why WordPress developers walk another way - this is, how it should be! :)
I have launched over 100 websites on WordPress - and they all have this plugin.
Thanks again!

Thanks!

Preserves the category hierarchy on the post editing screen

newvibe

Must use Classic Editor plugin – Add to my list of gripes with Gutenberg that it uses the REST API to display the categories, adding nothing to the categories box for the user while rendering the wp_terms_checklist_args filter useless. If you don’t already use the Classic Editor plugin (installed more than 5 million times to date), you’ll have to use it for this plugin to work. I’m looking for a work-around…
Does your list of categories go on and on, making it difficult to scroll to and find what you need? This plugin will collapse groups of subcategories into expandable submenus, which you may open and close as needed, cutting your category list down to a manageable size. Submenus with checked categories are not collapsed (but are collapsible), so you won’t have to hunt for them.
Thanks to scribu for the code from his Category Checklist Tree plugin, which prevents the breaking of the category list heirarchy.
This plugin works with post categories and WooCommerce product categories too. According to users, it works with custom taxonomies!
Links: <a href="https://www.newvibewebdesign.com/collapsible-categories-in-admin-for-wordpress/" rel="nofollow ugc">Plugin News</a> | <a href="http://newvibewebdesign.com" rel="nofollow ugc">Author’s Site</a>

Collapsible Categories in the Dashboard

In the Dashboard, collapses sub categories into hidden submenus that can be expanded and collapsed.  Keeps selected categories visible.

Category Checklist Tree vs Collapsible Categories in the Dashboard