I have a single post layout for a CPT called “artist”. I have a taxonomy called “artist-discipline” that accepts parent and children(sub) categories.
When displaying the single post view for the CPT, I need to display these where they appear related, for example:
Dance:  Ballroom, General, Hip Hop, Jazz
Design:  General, Graphic
Here is a mock-up post on my development server: https://wordpress-126964-3439916.cloudwaysapps.com/artist/test-one/
I’ve created two snippets running also based on research on this site. This first one is for getting the parent category with loopers
/**
 * Get parent category with Loopers
 */
  
  add_filter('cs_looper_custom_parentcat', function($result, $args) 
 {
 
$category = get_queried_object();
 
  $cat_args = array(
'hide_empty' => 1,
 'parent' => 0,
'taxonomy' => 'artist-discipline'
  );
  
  $parentcats = get_categories($cat_args);
return $parentcats;
}, 10, 2);
This one to get children.
    /**
     * Get sub category with Loopers
     */
    add_filter('cs_looper_custom_subcat', function($result, $args) {
        
        $cat_args = get_categories(array(
            'taxonomy'=> 'artist-discipline',
            'hide_empty'=> 1,
            'parent'=> get_queried_object_id(),
            'orderby' => 'name',
            'order' => 'ASC'
        ));
        return $cat_args;
    }, 10, 2);
I will provide credentials in secure note.