Using the Note field
You can add notes to any contact in Address Book. This makes it easy to keep track of details about a person in your address book.
Select the person in the Name column in Address Book, then click the Note field in the card.
The Note field can be edited at any time, even if the card is not in edit mode.
You could make a dedicated field that requires the edit button...
Using custom labels
You can change the label that appears next to a piece of information on a contact's card. For example, you might want to change "work" to "support" next to a phone number.
Select the contact that you want to change.
Click the Edit button at the bottom of the window.
Click the label next to a field, then choose Custom from the pop-up menu.
Enter a new label for the field.
The new custom label appears on this contact's card only.
If you want to change a specific label on all cards in your Address Book, edit the card template. Choose Address Book > Preferences and click Template. The Template pane also allows you to add other types of fields on contact cards, such as a nickname, job title, birthday, anniversary, and URL. Use the Add Field menu.