Can't create keyboard shortcut for "New Record"

I’ve tried to create a new keyboard shortcut for Sheets>New Record and can’t. I’ve tried using control-option-command J, which doesn’t conflict with anything else (as far as I can tell). For the menu title I put in “New Record”. When I try to use the shortcut, all I get is the unhappy alert sound and nothing happens.

Is it possible to create a keyboard shortcut for New Record and am I doing something wrong (I hope)? If not, could one be added? It used to be command-R which I know conflicts with the command for Reveal now, but could it be something else? A keyboard shortcut is very useful when I’m adding several new records to a sheet.

Thanks!

This menu item is created on startup, maybe the system preferences don’t support this or the menu has to be pulled down at least once. The only workaround coming to my mind is to use the toolbar item instead.