Now you can add multiple products which have no options by using checkboxes with product quantity and click on single button.
First select the products from category by checking checkboxes and you see the total amount of product you selected in sub total field than click on "Add all in cart" button of sub total.Selected product add in cart with their selected quantity.
1). Checkboxes comes only for those products which have no options.
2). Only those products will be added which do not required options. Because product which required options first it selected for add to cart.
3). This work on default theme perfectly but if you use on different theme need some changes.
4). If have any query can do mail on email@example.com or comment below.