There is an input hierarchy or stack in place, player controller is the top I believe, UMG Widgets can be pushed to the top.
If the player controller doesn’t have an InputAction using a certain key then the possessed actor takes the input and checks if it has an action using that key, if it does it performs the action. When you create an InputAction in your Project Settings it is available in all actor blueprints and PlayerController so there is no need to pass inputs, just put them in the right place