Hello ShaneMcD,
We have a great support article that might help with this. It outlines all the ways you can work with your Contacts list on your Mac. Please take a look at it here: Create and change lists in Contacts on Mac - Apple Support. Follow this guidance:
- "In the Contacts app on your Mac, select one or more contacts listed in the sidebar.
- There’s no limit to the number of contacts you can add to a list. If you use more than one account in Contacts, make sure the contacts you select are in the same account.
- Drag the selected contacts to a list in the sidebar.
- If the contacts aren’t added to the list, check if it’s a Smart List—you can’t add contacts to a Smart List.
If you use an Exchange account in Contacts, those contacts can belong to only one folder at a time. Any contacts that aren’t in a folder you create are in the default Exchange Contacts folder."
If this is not working as expected (as explained above), a simple restart might help resolve the behavior as well. Follow this page: Shut down or restart your Mac - Apple Support.
We hope this helps. Let us know if we can assist with anything else at all. Take care.