//Enabling custom post type 'tunnelvente' for designing offer pages
function wfocu_allow_cpt_for_offer_design( $args ) {
	$cpt_slugs    = array( 'tunnelvente' ); //Enter your own slug(s) here to white list them
	$allowed_post = $args['post_type'];

	$args['post_type'] = array_unique( array_merge( $allowed_post, $cpt_slugs ) );

	return $args;
}

add_filter( 'wfocu_allow_cpt_for_design', 'wfocu_allow_cpt_for_offer_design', 10, 1 );