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.

shawfactor

This plugin extends the default taxonomy functionality and extends it to users, while automating all the boilerplate code.
Once activated, you can register user taxonomies using the following code:
<pre><code>register_taxonomy('profession', 'user', array(
 'public' =>true,
 'single_value' => false,
 'show_admin_column' => true,
 'labels' =>array(
 'name' =>'Professions',
 'singular_name' =>'Profession',
 'menu_name' =>'Professions',
 'search_items' =>'Search Professions',
 'popular_items' =>'Popular Professions',
 'all_items' =>'All Professions',
 'edit_item' =>'Edit Profession',
 'update_item' =>'Update Profession',
 'add_new_item' =>'Add New Profession',
 'new_item_name' =>'New Profession Name',
 'separate_items_with_commas'=>'Separate professions with commas',
 'add_or_remove_items' =>'Add or remove professions',
 'choose_from_most_used' =>'Choose from the most popular professions',
 ),
 'rewrite' =>array(
 'with_front' =>true,
 'slug' =>'author/profession',
 ),
 'capabilities' => array(
 'manage_terms' =>'edit_users',
 'edit_terms' =>'edit_users',
 'delete_terms' =>'edit_users',
 'assign_terms' =>'read',
 ),
));
</code></pre>
Read more about <a href="https://codex.wordpress.org/Function_Reference/register_taxonomy" rel="nofollow ugc">registering taxonomies in the codex</a> 
This is heavily inspired by previous work by <a href="http://justintadlock.com/archives/2011/10/20/custom-user-taxonomies-in-wordpress" rel="nofollow ugc">Justin Tadlock</a> and also forks Damian Gostomskis plugin in the repository to add additional functionality, including:
<ul>
<li>Fixes a bug with display of existing user taxonomies in the user-edit screen</li>
<li>Fixes a bug with taxonomy count in the old plugin where deleting users did not update the count</li>
<li>Add support for ‘single_value’ attribute when registering a user taxonomy for taxonomies which should only have one value.</li>
<li>Properly supports the capabilities associated with the taxonomy when registered.</li>
<li>Supports ‘show_admin_column’ attribute when registering the taxonomy in the same way as post taxonomies.</li>
<li>Where ‘show_admin_column’ is true admins can assign user taxonomies using bulk edit functionality.</li>
</ul>
Check out <a href="https://lhero.org/portfolio/lh-user-taxonomies/" rel="nofollow ugc">our documentation</a> for more information on how to register user taxonomies.
Like this plugin? Please consider <a href="https://wordpress.org/support/view/plugin-reviews/lh-user-taxonomies/" rel="ugc">leaving a 5-star review</a>.
Love this plugin or want to help the LocalHero Project? Please consider <a href="https://lhero.org/portfolio/lh-user-taxonomies/" rel="nofollow ugc">making a donation</a>.

LH User Taxonomies

Perfect

Great one

I can confirm that this plugin works with WordPress 5.4 and is really good.

Works with 5.4

Thanks Pete for this super plugin.

Pete also updated the plugin based on feedback.

I am using it as part of a members site.

Thank you!

Regards
Mike


Super Plugin, Responsive Developer

Excellent plugin, thanks. One thing I'm adding to my implementation is to expose the taxonomy via API.

register_taxonomy('profession', 'user', array(
  ...
  'show_in_rest'          => true,
  'rest_base'             => 'profession,
  'rest_controller_class' => 'WP_REST_Terms_Controller',
));

Solves my problem

Simplify the process of adding support for custom taxonomies for Users. Just use register_taxonomy and everything else is taken care of.

Drop-down-taxonomy vs LH User Taxonomies