As i was testing the latest built 1638 i came across when "GROUP DONE" button doesn't work after you select your final modified item. Let's say you have 2 different modifiers 1st modifier GROUP DONE works but when you go the the second modifier "GROUP DONE" doesn't work. If you have only 1 modifier it doesn't work again. But instead you can use "DONE" button under listed item's section.
Is it a mistake / bug / changes don't know.