Create multiple taxonomies with custom fields values on the fly when creating new posts

This is the code I use to insert a list of taxonomy terms in a dedicated plugin category. On can also directly add the terms to the main post category.

    // ************** Add taxonomy

    $taxonomy_term = "my_term";
    $taxonomy_category = "my_taxonomy_category";

    if (null !==(get_the_ID())) {

        if ( taxonomy_exists( $taxonomy_category ) ){

            // if the tag doesn't exist
            if ( ! $term = term_exists( $taxonomy_term, $taxonomy_category ) ) 
                // insert it and get its id
                $term = wp_insert_term($taxonomy_term, $taxonomy_category, array() );

            // Create a list of plugin tags meant to be inserted into dedicated plugin category
            $list_taxonomy_term .= $taxonomy_term . ", " ;

        }
    }
    if ( $term && !is_wp_error( $term ) ) {

        // Link terms to plugin dedicated category
        wp_set_post_terms(get_the_ID(), $list_taxonomy_term, $taxonomy_category, true);  

        // Add plugin tags to the current WordPress post main taxonomy if we want so
        # wp_set_post_tags(get_the_ID(), $list_taxonomy_term, 'post_tag', true); 

    }