Originally Posted By: MeStinkBAD
It's cntrl-z/cntrl shift-z for undo/redo...

1. Open a script in the Script Editor.
2. Alter the file (like add a space at the end of a line).
3. Click the Check Brackets button, or one of the other options that Wims has said.
4. Click Edit, and you will see that the Undo/Redo are disabled. Same goes with CTRL+Z and CTRL+Y.

Also, no such thing as CTRL+SHIFT+Z

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