Yoren Chang

Thanks to <a href="https://github.com/WebDevStudios/Taxonomy_Single_Term" rel="nofollow ugc">Taxonomy_Single_Term</a>, a library created by <a href="http://webdevstudios.com/" rel="nofollow ugc">WebDevStudios</a>, it made my work much easier on creating this plugin.
With Categories Metabox Enhanced, you can:
<ul>
<li>Change the built-in Categories metabox/panel to a single term UI, which means replacing the checkboxes with radio buttons or a select drop-down.</li>
<li>Apply the single term UI to other hierarchical taxonomies in the plugin’s Settings page.</li>
<li>Customized the single term UI by setting these options:
<ul>
<li>Priority and position of the metabox placement.</li>
<li>Title of the metabox.</li>
<li>If child-terms should be indenting.</li>
<li>If adding of new terms from the metabox is enable.</li>
</ul>
</li>
</ul>

Categories Metabox Enhanced

Replace the checkboxes with radio buttons or a select drop-down in the built-in Categories metabox and Gutenberg sidebar panel.

Themepure

The Pure Metafields Plugin is a powerful tool designed to enhance the functionality and flexibility of your WordPress website. With this plugin, you can easily create and manage custom meta boxes, adding extra fields and data to your posts, pages, and custom post types.
<h3>Key Features</h3>
✅ Custom Meta Boxes: Create unlimited custom meta boxes with ease. Define the title, placement, and priority of each meta box to suit your needs.
✅ Flexible Field Types: The plugin offers a wide range of field types to choose from, including text, textarea, select, checkbox, radio buttons, date picker, and more. Customize the field options and validation rules effortlessly.
✅ Repeatable Fields: Enable the ability to repeat fields, allowing users to add multiple instances of the same field dynamically. Perfect for scenarios where you need to capture multiple sets of data.
✅ Conditional Logic: Set up conditional logic to show or hide fields based on the value of other fields. This feature adds versatility and improves the user experience of your forms.
✅ Built-in Validation: Ensure data accuracy by implementing validation rules for your fields. You can define required fields, validate input formats, and customize error messages effortlessly.
✅ Save and Retrieve Meta Data: The plugin provides simple functions to save and retrieve meta data, allowing you to access and utilize the stored information in your themes or plugins.
✅ Integration with WordPress API: Seamlessly integrate with the WordPress API and extend its functionalities. Hook into actions and filters to manipulate meta data and create dynamic interactions.
<a href="https://themepure.net/plugins/puremetafields/" rel="nofollow ugc">Live Docs</a>

Pure Metafields

Very light weight playable plugin

Pure Metafields is very light weight plugin tused to create custom metabox for any post type like page, post and your custom post type support it.

Categories Metabox Enhanced vs Pure Metafields