You can undo or redo an action in your Clipchamp video by clicking the back or forward arrows in the top left-hand corner of the Timeline. You can undo about 50 actions.
Alternatively, you can use your keyboard to edit faster. To Undo, use Control + Z (Ctrl + Z) on your keyboard. To Redo, use Control + R (Ctrl + R) on your keyboard.
This key combination is the same for both Mac and PC users.
If you're a Mac user, command + Z won't work in Clipchamp. You must use the Control key + Z.