This is already possible to do.
I know it is possible because I have done it before.
But try as I might right now, nothing is happening - all dimensions are 0.
I know you don't need to use gravity (there is not an option for stairs anyway).
I have the grid fill on (just in case it needed that), but the stair does not pre-select when I hover over it.
I have obviously turned something off, but I have no idea what it is.
I have tried a default GS template as well and no joy there either.
One of the forum moderators.
Versions 6.5 to 25
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10