Suppressing the Notification

Disable all the Carriers at once

This is the best approach if you have to test the specific Notification, instead of a single Carrier.

To do this, you should use the filter:

add_filter( 'notification/should_send', function( $should_send, $notification, $trigger ) {
if ( $something ) {
$should_send = false;
}
return $should_send;
}, 10, 3 );

At this point, the Trigger doesn't executed the action() method so you cannot use the Merge Tags. If you rely on Merge Tags, suppress the Carrier instead.