NotificationSubsystem

Where all the logic.

You can call NotificationSubsystem anywhere in the project.

This NotificationSubsystem is inherited from UGameInstanceSubsystem, which means that this would only be initiated once per game instance and will have consistent data when loading level or switching sessions.

This holds the queue and is responsible for handling added/removed notifications.

If you need to bind a delegate each time a notification is added/removed, there are event dispatchers there that you can bind to.

You can also get the entire queue, or get the currently displayed notification.