It wastes space and limits how many room locations or systems you can see at-a-glance which can lead to errors when rooms are checked that are not in the window view.

Dragging an item from an explorer to the "Add" zone is pointless. You can just drag into the project vs. all the way over to the top right corner of the screen.

Dragging an item within a project to the "Assign" box is pointless. It is far faster, more efficient and ergonomic to use the Control+D shortcut to clone an item into any location or system especially given the fact that when you have a lot of rooms and systems, you cannot see them all because the drop zone is taking up so much space.