How to set up an AppleID Recovery Key for a non main AppleID?

I have several Apple IDs that I use to share information between my Macs.... There is the main one I use for calendar, messages, email, etc., but also another AppleID I use to share specific groups of contacts of different types... I've set up a Recovery Key for my main AppleID, but can't figure out how to do it for the others, as they are not accessed via the AppleID system settings that the main one is. Is there any way to do this?