Hello and welcome to the Forum!
To edit Buildings in your Castle you just need to click on this button: https://www.screencast.com/t/heaoNcApBo5m
Then you will be able to move, destroy, rotate and upgrade your Fortifications: https://www.screencast.com/t/plrpkl2SY6Om
Yep. Would be nice if there was like a temporary storage spot where you could put stuff if you don't have space while moving things around, but I suppose it might be hard to program into the game.I think his problem is that he has a full perimeter, but one Tower is badly placed so only 3 squares are vacant and he needs 4
It is often very difficult to click on a specific section of wall to slide it one square to the left or right
The only solution is to destroy and rebuild