Hello,

I want to write a custom world generator, but I don't want to override default generator - user should be able to generate world with vanilla generator without disabling/deleting the mod from mods directory.

I started researching where to start, but the information on the internet seems to be outdated. What is the best way to achieve it?

Do you mean like the "World Type" button in the "Create New World Screen"? e.g. flat, large biomes, etc.

It's not something I have looked at in recent versions.

But you should look at WorldPreset which has a vanilla registry key in the Registry class you can use for DeferredRegister.

 

I believe you can also add them with using the datapack mechanism if you only want to resuse vanilla logic.

The only thing I can find on the json format (beyond reading the codec) is this? https://misode.github.io/worldgen/world-preset/