Text editing controls in iOS have been, shall we say, a mixed bag since it was called iPhone OS. In iOS 13, we now have a simple, dedicated gesture to toggle an editing toolbar: a three-finger tap. Well, more like a ‘tap and wait a beat’ gesture.
This displays a toolbar at the top of your device with controls for undo, cut, copy, paste, and redo.
It works in most apps I’ve tried: Messages, Safari, Slack (surprisingly), Tweetbot, and Keep It, but not Things (also surprisingly).