Is there any tool to edit custom maps? I know there's the builtin map generator, but imo, it just doesn't give you enough control over the outcome. I want to be able to add/delete planets/stars at will, exactly where I want them. I also want to at least give each side some starting structures and units. Restricting the available techs would be nice too.
I know such a thing must exist, since some of the non-random maps have a very exact and specific layout, but is the tool internal-only, or is it publically available somewhere?

Edit: I guess I should've checked the modding forum first. Found a description of the .galaxy file format in there,