Behaviour I'm used to from 1.x:
- use-item-groups toggles whether the items in menus are separated by category (logistics/production/fluids/etc) or whether they all appear on one screen.
- use-item-subgroups toggles whether the items are separated by rows (e.g. inserters on one, belts on another) or whether they're all combined together into one group similarly to how they appear in inventories.
- use-item-groups has no effect
- use-item-subgroups toggles both of the aforementioned effects simultaneously