Create "Custom Tag" for CPT.php

/*** Create "Event Tag" for Event CPT
–––––––––––––––––––––––––––––––––––––––––––––––––– ***/
function create_event_tags_taxonomy() {
    register_taxonomy(
        'event_tags',  // Taxonomy key
        'event',       // Post type name
        array(
            'label' => __( 'Event Tags' ),
            'rewrite' => array( 'slug' => 'event-tag' ),
            'hierarchical' => false, // Set to false for tags, true for categories
            'show_in_rest' => true,  // Important for block editor/Gutenberg
        )
    );
}
add_action( 'init', 'create_event_tags_taxonomy', 0 );