Regarding my lengthy comment above, I’ll just add that the Handled / Unhandled here is what controls how the Widget and the Player Controller respond to the input.
Essentially, if you pass Handled, you’re indicating you’re done with input processing and nothing else should receive it. If you pass Unhandled, the input will check for other widgets underneath and if it finds nothing that could Handle it, the input will be passed on to the Player Controller.
The above assumes we’re using Input Mode Game and UI.