Please add a delete all stored notifications from an application.
Occasionally from a device I don't use often, when I open it, it tries to sync 10s of thousands of old messages even though message retention is only set to 250 on that device. The app crashes due to this high volume of syncing. The only fix is to uninstall the Pushover app completely on that device and reinstall. It would be nice to be able to purge all notifications from an application instead.