To add the vehicle category in the vehicle detail permalink, add the below code in the child theme’s functions.php.

add_filter( 'cdhl_cars_cpt_cars', 'cardealer_child_extend_cpt_cars' );
function cardealer_child_extend_cpt_cars( $args ) {
	$args['rewrite']['permastruct'] = '/vehicles/%vehicle_cat%/%postname%';
	// The above structure will generate the URLs of the vehicle detail as below.
	// For "cars" category: https://example.com/vehicles/cars/chevrolets-dart/ ()
	// For "bikes" category: https://example.com/vehicles/bikes/suzuki-gr-150/
	return $args;
}

You can adjust the code as per your requirements.