In Safari there's an always active "double tap to zoom" that's kind of fantastic.
No use as is in Affinity Designer because most tools need context of taps to be theirs.
BUT when holding down the SpaceBar (activating the hand/pan tool) it would be super handy to have double tap to zoom into the point that's being double tapped on.
Perhaps a 5x increase in zoom. And a setting somewhere to set this amount of zoom. So users could set it to 2x, 10x, whatever they want.
// Spitballing and Spamming feature requests is more fun than I dare admit.