Pigrecolab

This plugin adds radiobuttons near every category (even if you add a new category) so you can choose the primary category of your post **. Selecting a primary category and updating the post saves this data into a custom field with a meta key of “primary_category”.
To display a list of all posts with a particular primary category, use the shortcode [primary-category name=”CATEGORY NAME” post_type=”POST TYPE”] where CATEGORY NAME is the name of the primary category you wish to display and POST TYPE is the custom post type name. If a name is not specified, the shortcode will default to all posts with “uncategorized” set as the primary category. images or post.

Primary Category

WordPress plugin for setting and displaying primary categories for posts and custom post types. This is a fork from Jacob McKinney's Primary Cate …

denizozsen

Features: 
* Ability to designate a primary category for posts and custom post types. 
* Supports custom post types and custom taxonomies with hierarchical structure. 
* Category in permalink is the primary category, if one is set. 
* Shortcode for displaying posts with a specific primary category. 
* CLI command for listing posts with a specific primary category.

Select Primary Category

Adds the ability to designate a primary category for posts and custom post types.

Primary Category vs Select Primary Category