Lack of visual separation when they are from the same app

This is best explained with a screenshot:

It would be nice if we'd have some visual separation between the two missed calls here too.

@snwh would that be something you could look at? This can be reproduced via

notify-send -A 'call back'  -a org.gnome.Calls call1 missed
notify-send -A 'call back'  -a org.gnome.Calls call2 missed
notify-send -a org.gnome.AnotherApp message