Hi,
I’m using HTML5 notification using google gcm.
They works well but not that well.
If I read a notification from my PC, this isn’t canceled on my phone and on my laptop.
Since I access HA from three devices, if I get a notification, I get it on every devices and when I read a notification this isn’t canceled on the other devices.
This is pretty unconvenient.
If I remember right, last I check, that’s not possible to cancel a html5 notification the way you wanted once it’s sent to your device(s).
If you really want to try, maybe set up the notification automation based on your presence, to send target html5 notification only to the device you are on, rather than to all devices. But that creates other limitations/inconvenience as well.