This is documentation for Mathematica 3, which was
based on an earlier version of the Wolfram Language.
View current documentation (Version 11.2)
 Documentation / Mathematica / Other Information / Menu Commands / Edit Menu  /
Undo

▪ Undo reverses the previous action.
▪ You can only undo your most recent command. In general, you can undo the basic commands in the Edit menu, and any amount of typing you have done since your last action.
▪ The only way to undo several actions at once is to go back to an earlier version of your file: close the file, click No when asked if you want to save the changes, then reopen it. The notebook then reverts to the last version saved.
▪ Keyboard shortcuts: z ; z z