I thought that system could only be generated procedurally and system are in fact just parameters to generate the planets but I saw this system from RLM: the "Boss System". This system has visibly not been procedurally generated with test texture, not randomly placed element, water on fire, etc. Does this mean there is a hope to make fully custom planets ?
Those are just special biomes included into the game by default. Biomes do support direct placement of brushes, that's what my hack of a mapeditor does. (https://forums.uberent.com/threads/wip-mapeditor.65201/) But I think Uber is working on exactly that as well right now.
Thank for your answer ! I hope you're true when you say that Uber is working on this right now (and not "just" symmetrical system).
Between the current and the last patch there was some, not yet used, code added that indicates the system editor soon will have components very similar to my mapeditor and in some of jables updates it was stated as well. I am pretty sure we will see this stuff sooner than later