To register a Universe, you need to create a JSON file at data/corewithstuff/cws_universes/universename.json

Example JSON

{
  "id": "modid:universe_name", // Universe ID. Optional; without it, the JSON filename becomes the ID.
  "display_name": "Universe Display Name", // Name shown to players.
  "dimension": "modid:universe_dimension", // Dimension used for the universe.
  "removed": false, // True deletes this universe. Only "id" is read alongside it.
  "boundary_radius": 2000000.0, // Horizontal universe boundary. Minimum is 1000.
  "transition_height": 1850.0, // Vertical transition threshold. Minimum is 128. Button only galaxy exit does not eject players at this Y level.
  "ambient_color": "#FF090B18" // Universe ambient color in ARGB format.
}