Minecraft mod interact with inventory?

I just want to make a mod that can interact with an inventory (e.g. Navigator). I would need this to do an "auto-join". With auto-join, the player xy should automatically join in a game mode on Gomme (e.g. TTT)

Can someone help me there?

I would have a player file created in the plugins folder. E.g. Yml or Json

Then you just have to create a menu by choosing which mode you want to have or a ChatCommand.

After that you just have to do an onJoinEvent that teleports you into the right world.