Well obviously you go into settings, then general, then multitasking even though it's not really multitasking, and then you notice that under the gestures on/of

Well obviously you go into settings, then general, then multitasking even though it's not really multitasking, and then you notice that under the gestures on/off slider thing there's a description of the 4/5 finger gestures. Btw the others are pinch to home screen and swipe up to app switcher. I only knew about the swipe left/right one .. I think I probably saw it on an advert maybe? I have no idea how you're supposed to discover it.