Import one WED into another WED

I'd like to create some rooms and then import them into another WED. I want to be able to alter the imported WED so I don't want to save it as an Entity and have to shell out to change the room in. Is this possible?

Is it possible to add things to the prefabs?

since prefabs are .wmp files.. yeah, this should work

I'd look where the prefabs are saved and create another folder.