Currently, Xrm.App.addGlobalNotification() does not allow the user to specify an ID for the notification.
An ID is provided by the platform inside the Success function of the returned promise, however, at that point, it is too late to reference the ID inside the action for the notification, which must be defined before the function is called.
Ideally, users should be allowed to specify a uniqueID, similar to Control.addNotification(). This would allow us to call addGlobalNotification multiple times with the same ID, without multiple copies of the same notification being added to the App header.
At a minimum though, at least supply the ID as a parameter inside the notification.action.eventHandler function, so that the notification can be closed when the user clicks the Action button.