I've been working on a project called Submaniac, a program to manage Subnautica installations.
It manages several installs of the game. You could want an install with the vanilla game, a game with tons of cheats with QMods, a game with not very cheaty mods, and a game with only mods that make it harder.
There's also one big problem with mods in Subnautica. QMods, the platform used by literally every mod except one, is completely incompatible with that one. And the incompatibility is Nitrox.
Nitrox is a MULTIPLAYER!! mod for Subnautica. I would give up all of my mods for Nitrox because it's so much fun. However, I don't have to because I made Submaniac.
Submaniac's menu defaults to the currently loaded save file. I switched to Nitrox and pressed enter, then it moved my old save into its directory, then moved my Nitrox save into the save directory. It then launched the game.
I might add a mod manager or game creator tool in the future, currently I have to create installs with Windows Explorer.
I'm going to go play Subnautica now.