I'm not sure if it's related to the new version...

When I make a staircase, I can't modify it anymore.

I tried several formats of staircase, in existing or new/blank instance of SH3D, but the result is the same. I can generate the staircase, and in the right-click pop-up menu Modify Furniture is available, but nothing happens. Same result when double-clicking the generated staircase.

I have sent the file to your email.