You can undo/redo actions when creating a workout. This is a handy tool if you realize something is wrong, and you want to "undo" to return to a previous stage or vice versa.
Here is a video that will show you how to undo/redo
Undo/redo does not work in relation to music files. If you replace a playlist or delete a playlist, you cannot use undo to get it back. You need to import the playlist again.
Undo/redo is placed in the top menu bar and you simply click them when needed.