Yes, I knew about RadzenNotification, I have using it, but I think (I've not tried yet) RadzenNotificationMessage can work alone without RadzenNotification (as I write before, I've not tried yet)
When I wrote about multiple messages I'm think about some new option to group messages by severity, I mean two-N messages with severity error can draw together like primeng can do with
<p-messages>. So that, I wrote about posibility to change NotificationMessage for
List<NotificationMessage> and grouped in presentations, all of that if it's posible and you find interesting.