Quick answer: Unreal SetInputModeGameOnly suppressing the Tab key globally? Game-only input mode disables Tab for UMG accessibility - use SetInputModeGameAndUI for partial UI accessibility.
Game uses Tab for inventory. Switching to game-only mode breaks Tab; players can't open inventory.
Use GameAndUI mode
Allows UI input alongside gameplay. Tab works for both contexts.
Or remap Tab
For pure-gameplay mode, use a different key for inventory. Removes the mode conflict.
Custom input mode
Subclass UInputModeBase. Customize per-key behavior. Heavy; precise.
“Input modes are coarse. Game-only is genuinely game-only.”
If your game uses UI-bound keys during gameplay, GameAndUI is the right mode. Game-only is for FPS-style total focus.