- Multiple controllers for local multiplayer don't really work as there are bugs between GZDoom and Steam Input.
- You need to have set the primary controller as player one as all the other players input will cause the inputs to loop sometimes. For example if you are docking the Steam Deck and want to use an external controller, set that controller as player 1 via Steam Input and not the Steam Deck.
- Pressing "Save configuration" within the GZDOOM options menu and you have mods that adds extra controls will wipe those extra controls. It is better just to set the inputs without pressing save as they still will be saved.
The controls here are described as an Xbox Layout style controller. Many mods have also more inputs then what is bindable on a controller, `L1` and `L2` are mostly free for those types of actions.