Intentionally keeping widgets in the game instance seems like a bad idea, and I’m not sure how reliable that will be in PIE. The Game Instance is often used as a last-resort place to store a widget when a player can’t be found.
A good place to store widgets and references to widget assets is in the HUD class, and you can properly give them owning players too. This matters a lot in multiplayer for example, so it’s a good habit to get into.