Do you think opening the iOS Control Centre is too difficult since the iOS 12 release (swipe a finger down from the top right corner to open it)? Then there is an easier way to do it using Accessibility settings. This is how.
Open Settings > General > Accessibility > AssistiveTouch and enable it.
Under Custom Actions, tap Single-Tap and pick Control Centre as the action to perform.
That's it. Now you will see a floating icon on your iPad/iPhone screen. You can move it to anywhere you like. Mine is in the middle of the right edge of the screen so I can reach it with my thumb. One tap on it opens Control Centre.
If there are other actions that you think are difficult to perform (like restarting an iPhone X or taking a screenshot ), you can set that up as an action for long tap or double-tap.