GoldSim provides an automated "undo" and "redo" capability for actions involving the manipulation of graphics. These are accessible from the main menu (Edit|Undo and Edit|Redo). Alternatively, you can use Ctrl+Z and Ctrl+Y for Undo and Redo, respectively.
The Undo function only operates on actions involving the manipulation of graphic objects, such as adding, moving or modifying graphics and text. It cannot Undo actions that affect the model itself (such as editing inputs to an element).
The "stack" of actions that can be undone is terminated as soon as you carry out an action which cannot be undone. For example, if you add a text object, then add a rectangle, and then edit its graphical properties, you can step backward and undo these actions. If you subsequently added a new element, however, the "stack" of graphical actions would be deleted (and could not be undone using the Undo function).
The Redo function is only available after you Undo an action. That is, its function is to reverse an Undo.