How to Play Offline Local Co-Op
Go to Custom Game.
Select Create at the top.
Select your mode and maps.
You will now be at the Player Slot Selection screen.
If you dont want randos joining, switch the lock at the top of the screen. the number shouldnt matter unless you want specific online friends to join.
Right Trigger on any controller to add a local Co-op player. There’s no keyboard co-op for obvious reasons.
Click on blank spaces to add AI, and then re-click that AI to modify their difficulty.