Well, the solution was painfully simple. Easier than anyone even guessed??
Here's the scoop (from: https://social.technet.microsoft.com/Forums -- thanks for the link Jayant!)
The shortcut key combination is stored in the shortcut link (.LNK file) itself; once the link has been deleted the shortcut key should be gone. It's my (somewhat vague) understanding that explorer.exe (which maintains your desktop) scans your Start menu and desktop icons looking for shortcut keys, and thereafter keeps them in memory until you log off or change them (or until explorer forgets them, as occasionally happens to me).
Have you logged off and back on since you recreated and deleted your desktop shortcut? This will close and restart explorer.exe, which should reset shortcut keys to those that are actually defined in a shortcut link somewhere.
I would have *SWORN* that I had logged off/rebooted and still had the issue. But apparently I never had because that immediately fixed the issue and CTRL+ALT+N is now once again functioning as desired.