Is there any undo/redo button in App Inventor 2? Surprisingly I haven't found any. Did I miss something?
App Inventor 1 used to have such buttons for the block editor:
Edit: this feature is available again in more recent versions, please see answers below.
Surprisingly UNDO / REDO buttons have been removed in App Inventor 2.
If I can remember correctly they were causing some issues when blocks were undone after removing. Here is the issue which you can star, if you want more advanced tools you should take a look at Java as App Inventor is only the very basics of coding.