How to Select Primary Category for Hestia Posts using Yoast?
A post can be assigned to multiple post categories. The Yoast plugin allows you to select a primary category for any post inside the editor.
Go to Categories and select multiple categories.
A dropdown for the primary category will appear.
Select a primary category for the post.
Even if the post has been assigned to multiple categories, having a primary category will control the related posts that appear.
📝 Note: The posts appearing in the related posts section don't need to have the same primary category but to have it among their assigned categories.
If you want posts from all the selected categories of a post to appear in the related posts section, use this filter:
add_filter( 'hestia_related_posts_by_yoast_primary_term', '__return_false' );