If you need to mark any of your Addresses temporarily or have them stand out from the rest of your addresses, you can use “gold stars.” These gold stars are small yellow star icons that you can use to mark your Addresses as “important.” Every address that you create will have a small star icon to the left of the address name.
Using Gold Stars
You can mark addresses with a gold star either when the Address is in editing mode, or when the address is being viewed in your Folder.
You can also view all of the addresses that have been marked with a gold star when you click on the tag icon at the top of your Address Book and choose the "Important" tag from the list. See the image below: