The Action History tracks the last changes that you made in a study. You can undo and redo the last changes using the Action History.
Click Action History. The Action History dialog appears, displaying the actions you have performed on your study. The most recent action you performed is at the end of the list.
Actions that have been undone are grayed out.
To undo or redo a series of actions, click on the action in the list that you want to undo or redo back to. The actions you click will be highlighted.
When you are finished selecting actions, click Undo or Redo.