Merge contact cards in Contacts on Mac
If you have more than one card for a contact in an account, you can merge the cards. Merging cards combines the cards and keeps all the unique information in a single card.
In the Contacts app on your Mac, do any of the following:
Look for duplicate cards and merge them: Choose Card > Look for Duplicates, then click Merge.
Merge duplicate cards: In the list of contacts, select the duplicate cards you want to merge, then choose Card > Merge Selected Cards.
When you use several accounts in Contacts, you may end up with several cards for a contact — for example, one card from Yahoo and one from Google. You can link the contact’s cards to streamline your list of contacts without merging the cards. See Link contacts.