You can undo and redo unlimited operations performed in the Game Notation on the current game since it was loaded.
Accessed on the Edit menu or via shortcut keystrokes.
HIARCS Chess Explorer maintains a record of all your changes to the current game notation since the game was loaded. This is extremely useful as it means you can Undo any mistakes you made in changing the Game Notation, equally you can Redo (reapply) changes made after an Undo provided you have not made other changes since you performed the Undo.
Please note the shortcut keystroke for common operations is also defined on the menu, you can use the keyboard shortcut to invoke the associated function. For example Cmd+Z for Undo, Cmd+Y for Redo.