By replace I mean, can I click on an item in the render window, and replace it with something in the ID menu list thing. I want to make a custom version of the Arcaneum, but I don't want the half walls, I've been through the RoomKits and I know there are pieces that should let me have just an open room, but I don't know how I'm suppose to replace the ones I don't want, short of manually - which would be simple, but the snapping seems messed up - I think the axis/grid is off or something, and I'm not really confident that I should be messing with that.
Is there a key to replace items? For smaller scale, could I select an apple then replace with a cabbage in the render window or something? Is there a hotkey or something I can use? Thanks.