Merging Contacts / macOS 12.6 between users

My wife and I share an iMAC.

We have separate macOS accounts and separate iCloud accounts.

We use Mail and a wide number of other applications Signal, Whatsapp, Messages, facetime, etc.

As a consequence of the above we each have our seperate iCloud "Contacts".

Is there a way to periodically merger or bulk transfer "Contacts" from one account to another ?

(I believe there is no way for two macOS accounts to share and synchronise a common "Contacts" register.

Maybe there is a third-party utility to share and synchronise (bulk "Contacts" export and import ?, rather than one by one - there are over a 1000 entries altogether)

Thanks for any help on this issue

Stuart