Can I up vote this.  it would be handy to have it built in. you could use this option for loot, monsters, traps, or whatever. 

That worked thanks.

ok so I cant have 4 part mesh like this in a prefab.  I would need to do some mesh merge or something.

so if I have a prefab made of a number of meshes, then I cant use the product?

for example, the column and wall is made of 2 or 4 parts each.  the top prefab doesn't have a mesh.  if I make one of the mesh objects the parent prefab, it's only 1/4 of the total mesh.  assume this would be a problem as well?  will try it out later tonight.

I should also point out, that when I try to swap out the prefabs in the scifi demo, both my prefab and the provided sci-fi prefab get generated, even though I have replaced all the stuff in the inspector with my own asset.