I'm using:
Debian bullseye with its MATE desktop environment
MATE caja 1.22.1
MATE Terminal 1.22.1
GNU nano, version 4.3
In nano, Redo is mapped to Meta+E. In Keyboard Preferences I have selected "German German (no dead keys)" and in the Keyboard Layout Options under Alt/Win key behaviour, I have selected Meta is mapped to Left Win.
When I press Alt+E in a nano running in a MATE Terminal, it opens the Edit menu of the terminal window. When I press Meta+E (that is, the left logo key and E) anywhere, Caja is opened to the home directory.
I have not found any way to disable either of these shortcuts to enable me to use nano's Undo function. In Preferences → Keyboard Shortcuts, the Meta+E shortcut (or Super, or Win, or Logo) is not listed. In MATE Terminal's Edit → Keyboard Shortcuts... the Alt+E shortcut is not listed.