The Scenario editor keeps track of the changes made to the current scenario, and lets you undo and redo up to 100 changes. For example, you can easily restore any changes made to request and response contents, or restore a deleted operation.
To undo the last action
Click 
Undo on the Scenario editor’s toolbar, or press Ctrl+Z. Repeat to undo more actions.
To redo an action that you undid
Click 
Redo on the Scenario editor’s toolbar, or press Ctrl+Shift+Z.