Are you supposed to be able to UNDO operations? I have several times now done something I wanted to do over again because it didn't turn out as expected. For instance, the HELP said, to recreate a dormer if it was too high. I tried to UNDO but the menu choice was greyed out. I tried removing the dormer, but it left the hole in the roof. I tried removing the hole and got a messed up roof. I tried UNDO on that and once again the button was greyed out.
Any advice would be appreciated.