A long, long, time ago (I can still remember), Forge used to automatically provide a config UI for mods using its config system. Alas, this was removed in the 1.13 rework. It would be nice to bring this back — I know people often have issues with CC:T's config files, and this might simplify things a bit.

I think for now, we only want to expose the client config and, when on a singleplayer world, the server config. We could probably allow OPs to change the server config, but it's definitely a bit more work.

It might be worth taking inspiration from Configured and ForgeConfigScreens, just for UX.

Create has a way of changing configs in-game and can even understand the configs of most mods too. It might be worth looking at how they do that too.