you can place a Staircase object on the lower of the connected floors. What annoys me is that all staircases have railings, and the height of the object is seen as the total including railing. That makes it very hard to connect with a half-height platform (landing) and with the upper floor, because I have to fiddle with the height until the intermediate point of the top stair is aligned with the correct height. I am "abusing" sh3d as a building modeller rather than an interior design modeller so...
I've been annoyed by this issue as well, so I support the request. @Rado, are you aware of another site where development is organized and bugs/FRs could be posted instead? This Sourceforge project is the one linked in the "About" popup of version 1.3.1.
Having upgraded to Ubuntu 20.04 LTS, I have PCManFM 1.3.1,libFM 1.3.1, behaviour is the same.
Directory ttree: mountpoint cannot be selected
sort order switches cross-window