I don't see a config file in the config folder

Versions

• Mod version: overworld_mirror-1.15.2-1.3.0.12.jar
• Minecraft version: 1.15.2
• Forge version: forge-1.15.2-31.1.18
• UTeamCore version: u_team_core-1.15.2-2.10.5.154

Its in the world configuration folder. Can be packed in the default configuration folder for modpacks.

I don't know where the "world" configuration folder is. I'm running Linux.

You mean in the Saves folder?

In the world. Linux has nothing to do with that.
Its the default way forge handles world only configuration files

Depends if its the client or the server. Where the world is saved. migt be ~minecraft/saves/WorldXYZ/config or ~server/world/serverconfig

Okay. There's still no file in there.

Have you started the world / server? Its only generated after that.

Yes, I see the folders /overworld/dimension/data, but there's no file in the /data folder

Thats the wrong folder. That saves internal data.
The config is in the world under serverconfig/overworldmirror-server.toml

Okay, found it.

So now I can move it to .minecraft/config and tweak it to my heart's desire?

No. It stays there. Its per world. It can be packed in the defaultconfig folder for modpacks (and will be copied on startup to the world/serverconfig folder. If you change somethings in the world config you need to delete the overworld mirror directory in the world so the new world settings will be generated.

Right. All I care about is making modpacks. I should have made that clear. Thanks.

Could you put the file in the usual config folder so us modpack devs will find it where we expect it to be?

Duplicate of #4 .

No its the new FORGE config system and I will use that. Please adapt to new mechanics.
It also does not make any sense that it is in the common config directory because the config there can be diffrent for each world.