Sorry. We had created that shortcut in testing in the office for 'Copy As No Superscripts' awhile back and I looked at it yesterday and thought it was a 'default' shortcut.
We created it by going into the Keyboard Shortcut preferences, scrolled down to 'Copy As No Superscripts' (which I believe was blank in the Windows version) and highlighted it and then selected 'Modify Shortcut' then entered Ctrl+Alt+O (Which was an available key combination) and then 'ok'.
This made a keyboard shortcut for 'Copy As No Superscripts'. I thought this could help make your workflow a little faster than the 'right click' and select 'copy as', wait for the drop down box and move over to select 'No Superscript' method that you mentioned at the beginning of this thread.