I image that this will probably be implemented at some point, but I thought I would make an official suggestion post on it just in case.
If a building/wall has finished the building phase and is “Completed”, you are not able to place doors/windows inside the wall as you can in the building phase. If you attempt to do so, you will simply place it next to the wall and not inside of it. Sometimes I find a need to place a door/window after my building is finished and it would be super convenient to be able to do this.
As always SUPER happy you guys are making this game and I LOVE it! Can’t wait for dwarves