Y axis locked for vehicle blocks ect?

[NETSCAPE]

I'm new to the editor. I notice you cannot enter a value into the Y axis field, which would translate to vertical position in the world.

 

You might ask why I'd want to do such a thing when you can click the "set on ground" button... well I want to put some boxes or vehicles on a ferry bridge or "docks" on the Volga. I also would like to position MGs within the city of Stalingrad that might need to be slightly above ground level, on rubble ect, in what I would view as optimal MG positions. The MG guys can sit in any of the normal ground level areas and I wouldn't be too disappointed... but the not being able to set a vehicle on a ferry bridge =