Undo the “Undo”?  This sounds silly, I know.  But silly things happen (frequently). 🙂

If you undo a step, you cannot undo the undo by applying another undo.   (Because Excel allows 16 undos by default, although you can modify this setting.)

So how to undo the undo?

It is basically “Redo”.  And what we need to do is “Ctrl+Y” or click on the “Redo” button on QAT.

In case you don’t have the “Redo” button on your QAT, simply add it to QAT.