Enrico Sorcinelli

Taxonomies Sortable allow to sort non-hierarchical taxonomy terms associated to objects by drag&drop them on the administration interface.
<h3>Usage</h3>
Once the plugin is installed you can make a taxonomy sortable in the following ways:
<ul>
<li>Programmatically by adding <code>'sortable' => true</code> argument in <code>register_taxonomy()</code>.</li>
<li>Programmatically by using <code>taxonomies_sortable</code> filter below.</li>
<li>Using the Settings->Taxonomies Sortable administration screen by selecting non-hierarchical taxonomies you want to make sortable.</li>
</ul>
Note that making a taxonomy sortable, implicitly means also setting <code>sort => true</code> for that taxonomy.
<h3>Hooks</h3>
<code>taxonomies_sortable</code>
Filter allowing to programmatically set sortable taxonomies.
<pre><code>apply_filters( 'taxonomies_sortable', array $taxonomies )
</code></pre>
<code>taxonomies_sortable_admin_settings</code>
Filter allowing to display or not the plugin settings page in the administration.
<pre><code>apply_filters( 'taxonomies_sortable_admin_settings', boolean $display )
</code></pre>

Taxonomies Sortable

Allows to sort taxonomy terms associated to objects.

HelgaTheViking

Replace the default taxonomy boxes with a custom metabox that uses radio buttons… effectively limiting each post to a single term in that taxonomy.
A plugin options page allows the user can select which taxonomies she’d like to switch to using the custom radio-button style metabox.
Originally based on the the <a href="https://github.com/stephenh1988/Radio-Buttons-for-Taxonomies" rel="nofollow ugc">class by Stephen Harris</a>
<h4>Support</h4>
Support is handled in the <a href="https://wordpress.org/support/plugin/radio-buttons-for-taxonomies" rel="ugc">WordPress forums</a>. Please note that support is limited and does not cover any custom implementation of the plugin. Before posting a question, read the <a href="https://wordpress.org/plugins/radio-buttons-for-taxonomies/#faq" rel="ugc">FAQ</a> and confirm that the problem still exists with a default theme and with all other plugins disabled.
Please report any bugs, errors, warnings, code problems to <a href="https://github.com/helgatheviking/Radio-Buttons-for-Taxonomies/issues" rel="nofollow ugc">Github</a>

Radio Buttons for Taxonomies

Thank you so much for this plugin, so easy to use and makes creating a single category situations much easier.

Oh this is a life saver!

JUST WORKS

Many thanks to the author for this great plugin. Does one things and does it very well. Works with classic editor and block editor.

5 stars is not enough. Works with Gutenberg

We've been using this plugin for longer than we can remember, never had any issues whatsoever, highly recommended!

Excellent

Replace the default taxonomy boxes with a custom metabox that uses radio buttons... effectively limiting each post to a single term in that taxonomy.

Taxonomies Sortable vs Radio Buttons for Taxonomies