Settings/Accessibility/Touch/Back Tap On my iPhone 8, partly because I have a cover that is hinged to cover the screen on the lefthand side, I find the app switcher, by pressing the left hand edge, not particularly easy. I could, and mostly have to, use the home button to bring up open apps, but even that I am not happy with as it is a bit clumsy. (I believe that the iPhone 11 allows you to swipe up from the bottom, not having a home button.) I discovered the Back Tap facility - simply tapping on the back of the device. It can be set to a wide variety of functions, including shortcuts, mute, scroll and lots more. I have set mine for Double Tap to bring up the app switcher and Triple Tap to Play/ Pause some radio channels I have set up as shortcuts. (The above is with iOS14.01, so I am uncertain which earlier system versions it applies to.) I hope that this is of interest to others.