Now back to the soffits. I found how to add them. But in two corners I also have upright soffits where the duct work goes upstairs.
How do I add them? Or is that something I do with the walls? Perhaps they are not called soffits.
Here is an image of what it looks like where the upright and ceiling soffits come together.
I'm new to design so pardon my questions if they are obvious.