That's really neat. Thanks for this WAS.
May I push a bit and ask if you could do something similar for Lights? I think it would be really awesome to have a light tool editor. For example copy the lights, paste them and be able to randomize their intensity and color based on a given range.
There are already tools for this in Maya for example, but when you export through FBX you cannot set the Radius, soft shadows, soft shadows samples, ect... Only the strength and color get carried in Terragen and having to use Maya for this is quite cumbersome!