The Undo History dialog shows you a list of the actions you have performed on a schematic in the current editing session. To access this dialog go the Edit - History… in the main application menu. You can revert the schematic design to any point in its Undo History simply by selecting an entry in the list and pressing the OK button.
SigmaStudio's undo mechanism uses system memory resources. You can empty the history and free these resources by pressing the Clear… button.
Most actions that you perform in the Schematic and Hardware Configuration tabs can be undone. For example, inserting or deleting a block, creating a wire, re-naming a block, or moving the screen location of a block. You can undo the most recent action by choosing Edit - Undo from the main menu or by using the keyboard shortcut, Ctrl-Z.
Undoing can also be undone. After undoing an action, you can redo it by choosing Edit - Redo from the main menu or by using the keyboard shortcut, Ctrl-Y or Ctrl-Shift-Z.