Niraj Chauhan

This plugin will help the user to add a drop-down-custom-taxonomy box with the help of small code on his desired location.
<h4>Options</h4>
just place this small code into your theme file and the drop-down box will appear on that page 
code: 
for example, if you want to display it on home page, 
then navigate to index.php, the inside that put this code, if you want to display the custom taxonomies, then just replace category with your custom taxonomy name.

Drop-down-taxonomy

This plugin will help the user to add a drop-down-custom-taxonomy box with the help of small code on his desired location.

Amit Sonkhiya

K.K.Agarwal

Gutenberg Editor already maintains the parent-child relationship when you select a category. So the child doesn’t move at the top in the category meta box. So this plugin isn’t required if you’re using the Gutenberg Editor.
Categories in Hierarchical Order plugin applies to WordPress Classic Post Editor only.
This plugin contains functionality to let you maintain default hierarchical order of categories when you select and save them for a post in your WordPress Admin Classic Post Editor.
The selected category/categories, to which a post belongs, are by default pushed at the top in the Category tab while saving the post. Whereas activating Categories in Hierarchical Order plugin will keep the position of selected category/categories unchanged as per their parent/child relationship.
For support, use support page available here or visit <a href="https://www.astech.solutions/wordpress-javascript-jquery-plugins/categories-hierarchical-order/" rel="nofollow ugc">the page</a> at our official website. A <a href="https://github.com/as-tx/categories-hierarchical-order" rel="nofollow ugc">GitHub repo</a> is also there to post issues, contribution and feature requests.

Categories in Hierarchical Order

Does exactly what you expect from this plugin. Nice!

Works great!

Does exactly what should be the default option in Wordpress, great! Sorely needed if you have many categories (possibly with very similar names) and rely on a complex hierarchy.

Great!

Perfect

Why is this not part of the WordPress core yet? This plugin fixed my ugly looking category structure! Thanks guys!

Brilliant!

Categories in Hierarchical Order plugin maintains the hierarchical order of categories list in the Category tab under your WordPress Admin Post Editor …

Drop-down-taxonomy vs Categories in Hierarchical Order