This is very frustrating and should not be happening because it says in the guide that you can use negative elevations.

It says so right here: http://www.sweethome3d.com/blog/2018/05 ... house.html

"The elevation of a level may also be negative to design a basement or foundations."

The answer must be something really simple that I'm missing...

I have raised the entire house and set the basement at 0, because I don't know what else to do. That will probably cause more issues when I have to draw the exterior landscape.

Now I need to draw a pit which is below the foundation, and I can't. Not without raising all the other levels again. I also need to draw drainage and pipes that are underground and I can't do that without being able to enter negative elevations.