I think the editor needs:
Vertex Snapping - Object snaps to nearest vertex. Makes placing crates on floors for example, really easy.
Rigid Body Placement - This is an idea I though up. You make a static object a rigid body, for example a branch. The branch falls to the ground, positioned like it would be in real life. The object is then made a static object, but stays where it fell. It is a lot easier then trying to rotate the branch so it looks like it is lying on the ground.
Benton