I am using x15 and have drawn a soffit that covers the entire kitchen ceiling. I wanted to add a ventilation register on the soffit, but was not able to place it when I tried. The register placed on a regular wall, but not on the soffit.
Is it possible to place items to soffits?
I also attempted using the 3D Solid Tools feature, but I ran into the same problem, I was not able to place the vent.
Attached are two images, one of my design, and the other is the inspiration.