Comands to help with designing a building, advice needed

Am attempting my first building and getting stuck fast here. Example: Placing a castle type roof on tower but no idea how to get the stairs to open a hole in the roof , so units can get to the top.
Floors only fit on top of wall so stairs have a gap between it and next floor…is that how it is suppose to be? Can I make walls different heights? Do walls always cover the whole floor area or can I limit it to only half that… small room on top of big room?
Think you all get the idea what I am looking for.

Unfortunately, I don’t think there is any way, besides designing the floor and battlements by hand with the second floor and slab tools.

I’m pretty sure if you erase the right blocks and place the stairs right you can get rid of any gaps.

Not unless the walls have roofs on them, but then there’s a height option.

You can always erase some number of blocks on the outside of the second floor before raising its walls, and then fill the gap with a roof on the first floor or another floor if you want.

Thanks, have been testing the different stuff - walls, roof, floor and slabs. For me slabs is tops but the rest is too a great degree worthless when designing anything more than a square building. Erase is worthless for anything other than floors so if you found you made a mistake later and need removing it you are stuffed.
This was why I hoped there are commands that assist building that was known to you pro builders to compensate for this.

I’m not sure for stairs, but you can place ladders in the inside wall and Heartlings will phase through roofs.