Visually distinguish between notifications with and without default action
$ notify-send 'Notif without default'
$ notify-send --action=default=123 'Notif with default'
Currently, there is no way to tell if a notification is clickable (has a default action) when the button is disabled.
The only way to tell is to hover over it and see if the cursor changes.
One idea would be to have a small icon indicating the fact the notification is clickable next to the close button like so: