Edge Block/Add Site Notification - How to Disable with GPO?

DefaultNotificationsSetting is the control for this requirement. Keep it in the mandatory Microsoft Edge template and set BlockNotifications, value 2. You do not need NotificationsBlockedForUrls with a wildcard; that policy is meant for URL-pattern exceptions, while NotificationsAllowedForUrls explicitly creates administrative allow exceptions.

The Add buttons are not a reliable indication of effective permission. Microsoft describes mandatory Edge policies as overriding user preferences, so validate the applied policy rather than the presence of those controls. On a test client, run gpupdate /force, restart Edge, open the Edge policy diagnostics page, and confirm DefaultNotificationsSetting appears with value 2, status OK, and the expected machine scope. Remove any configured NotificationsAllowedForUrls entries, then test a clean site that has no existing permission.

If the policy is absent or ineffective, check the profile type: Microsoft documents that this notification policy does not apply to profiles signed in with a personal Microsoft account.