I don't think wall deletion is implemented yet, but it would be great also to add an undo/redo mechanic in Building mode.

Also there was an incident where I selected my half-built house by accident within building mode, and somehow the house disappeared entirely. I wasn't able to find the house or the already placed items again after that. Had to do a quick reload on the last save file. :)

Yeah it's really easy to select things you didn't mean to and accidentally move/delete things. There is supposed to be a build mode overhaul coming soon so hopefully these problems get addressed with that :)

I think a pop up saying do you want to is fine, but undoing.. That just seems to hand holdy. We can always restart our days.

^ I do agree with that statement about the hand-holding. I think it'd just be nice to have one step undo/redo for the sake of a quick simple fix to correct mistakes. I think a pop-up may get too tedious rather, especially if you're looking to do a large build at one time.