Sometimes you realize the changes you made were not what you really wanted to do. The Undo command lets you undo the things you have done. You can also redo an operation if you like the changes you made after all.
For example, if you transpose your entire piece up a half-step and realize that you really liked it better in it's original position, you can undo the transpose. This will return the score to the condition it was in before you transposed it.
A multiple-layer undo/redo allows you to undo and redo thousands of actions. The Undo History feature displays all previous changes, making it easy to quickly revert to an earlier version of the file.
To Undo an Operation
Select the "Edit" tab and select Undo
Press CTRL+Z on the computer keyboard.
To Redo an Operation
Select "Edit" tab and click on Redo
Press CTRL+Y on the computer keyboard.
You can easily access "Undo & Redo" over the quick access toolbar.