About Undo and Redo
On the File toolbar menu click 
(or press Ctrl+Z) to undo the previous action and 
(or press Ctrl+Y) to reinstate the last undo action.
Undo availability
- EV File Properties dialog box (all pages except the Classes page)
- Variable Properties dialog box
- Region Browser dialog box
- Region Editor dialog box
- Line Properties dialog box (all actions except creating or deleting a Line)
- Creating and editing lines
- Creating and editing regions
- Creating and editing virtual surfaces
Changes within a dialog box are grouped as a single action.
Undo and redo history
Click on the arrows in or buttons to see the list of actions you can undo or redo.
If you undo an action that has been followed by one or more subsequent actions, you will undo all of the preceding actions.
All previous undo and redo actions are cleared from the list when you perform certain actions that cannot be undone. These include
- creating a new line, virtual surface or variable
- creating or editing Region classes, Species and Target classes
- adding or removing a data file from a fileset
The number of items in your undo history is governed by the available computer memory. Actions at the bottom of the list become unavailable as you surpass this limit.