Currently not supported via any configs in the mod. Has been suggested before though, and would consider it if I can figure out a clean way to implement it with the existing settings

Ok, thank you!

I asked something similar quite a while ago now. IIRC there's a workaround involving setting up "territories" that can have a unique spawn list (?) but I can't recall whether that was limited to planets, or could be set up in a radius from specific coordinates. (Nor do I remember how to set up territories, anymore). Meridius could probably tell you more about that on the Discord server, or someone else would know.