So in effect this map editor is nothing but a tease rather than a useful comprehensive feature. I wish they had released something more useful or nothing.
This editor is impractical, does not load any textures for planets nor does it load and texture original homeworld planets that the game generates. In addition, there is no way to place and determine mionor races either.
It is crap at this point and I doubt there will be any new patch and/or improvement releases for this.
I wouldn't go that far... it is minimally usable and provides a way for people to create something for sandbox mode where surfaces variety is strictly randomized (somehow) just as any others.
It's not crap cuz without anything of that sort you can't play with your favorite settings & situations besides the usual random factors.
I think SD devs know very well about this particular "flaw" and if the past is any indication, they will certainly upgrade the stuff to make the Map Editor more efficient and entirely compatible with DA, their own CustomPlanets.xml and whatever other features **we** all asked for over the last year or so.
I repeat; your Mars surfaces are the result of a clear choice UN-maded for every last planets created & present in the saved file. There is nothing else but a whole 7 TYPE possibilities to select... from left to right on the slider provided -- Uninhabitable, Habitable by All, and the five extremes. I should even insist that there IS a huge difference between DA & TA processing of textures.