I'm modeling a split level home in Home Designer Pro 2020. You enter the house onto a stair landing ("Entry Level") and then go down 3 steps to the "Main Level" or up about 13 steps to Level 2. The floor that actually exists at the entry level is limited to the stair landing itself. The rest of that level is designated as "open to below", which is how various tutorials said to set up a split level home.
Since the main floor is just a couple feet down, most of the walls in the various rooms start at the floor of the Main level, extend up thru the Entry level, and end at the bot