Flatten terrain

I must say, after now having tried Torque 3D Beta 5, I am totally impressed with all the new features, and the cool interface! Amazing stuff, really.

But there's one thing that I can't quite figure out: when using the "flatten" tool on terrains, how can I make the terrain flatten in a certain height (i.e. 10 meters height)? It seems to go further and further downwards. If there's water close by, it will sink into it.

If I remember correctly, TGEA had the option of setting desired height of terrain.

Thanks