lucky for you, only 1 is needed, unity explorer[thunderstore.io], that's all for this

Host a game, in object search under "unityobject" search for the object class called "selectablelevel", after doing so choose 1 moon, then open it, modify the stats to your choosing, almost all moon statistics are self-explanitory, you can change the scene name to any avaible scene but i don't suggest choosing anything other than a normal moon's exterior(Level1Experimentation, Level2Assurance, Level3Vow, CompanyBuilding, Level4March, Level5Rend, Level6dine, Level7Offense, Level8Titan, Level9Artifice, Level10Adamance, Level11Embrion), other scenes load but they very break the game. I suggest method 1 if you want to select the moon easily, and are okay with replacing a moon, doing this you can also fix liquidation so you can actually land there, all of the base moons are ExperimentationLevel, AssuranceLevel, VowLevel, MarchLevel, RendLevel, DineLevel, TitanLevel, ArtificeLevel, AdamanceLevel, EmbrionLevel, LiquidationLevel, and TestAllEnemies

This one is a bit crazier than method 1, but better if you know how to properly build the stats from scratch. select any level, scroll down until you reach the methods areas, and click "evaluate(1)" on the thing called "SelectableLevel.SelectableLevel()", then reload the search bar on selectable levels. If done correctly there should be a new level that has a placeholder name called "untitled" that's grayed out and italicized. from here, start modifying it to your liking, i only suggest this if you are willing to put the work into something that won't even save, your level will not be selectable, you'll need to modify the round manager, time and weather manager, and the player manager the selected moon, you are unable to add this to the moon id's so you'll need to trigger the start of round manager to force the full loading process unless you change the id to an acceptable value(0-13), did I forget to mention people with no mods at all can still join you?