I think it would be really good to have categories, I offer services and I offer classes, it would be good to be able to put all my booking types for classes in one category and my booking types for services for another, furthermore, it would be good to be able to do sub-categories as well, so I can separate all my services in subcategories, whenever I have to update booking types I have to scroll the a list of all my booking types to find the one that I'm looking for.