Add more than one service/product at a time

During checkout, when adding services/products it would be extremely helpful and time saving if we could add multiple things at once. When a client adds a cut to a color service and then purchases three products I have to manually add four different things to the checkout screen, one at a time, and it is so time consuming. Would love if I could just click on all the things I want to add then hit an ADD ITEMS button.