In mark-hotkeys.lua you add a bunch of prototypes of type custom-input. You then go on to specify a property consuming = "script-only". That should probably be consuming = "none". The other valid value would be "game-only". And the reason you'd want to use that is if you wanted your input key to override the same input key if it's used for the base game. "none" says you want both to happen if the same input key is mapped to both a base-game action and an action in your mod.
