Suppress notification pop-ups in presentation mode

Presentation mode is very useful for stopping screen blanking and screensaver activation, but presentations can still be interrupted (and privacy compromised, especially in recorded screencasts) by notification pop-ups from apps including messaging systems such as WhatsApp, Slack, Mattermost. It would be extremely appreciated, and I think an expected behaviour, if presentation mode were also to deactivate XFCE notification pop-ups.