I have a macro that makes a notification every few minutes. Is there a way to clear all previous notifications for this macro (or if not, all of KM is fine) which I can run before making a new notification?
TIA!
... gentle bump
I just searched the forum and maybe this will be a starting point at least. I don't know anything about it though. 
The macOS Notifications API has very little access.
Keyboard Maestro can generate notifications, but it cannot manipulate them after the fact.
Some people on the forum have had some success using AppleScript on the Notifications Center.