In Notes 8.5.2, you can make a contact or group private, to hide it from anyone who has access to your contacts but not your mail. If someone has access to your mail, then he or she can see private contacts and groups.
To mark a new contact or group as private, click the Mark Private
check box when creating it.
To mark an existing contact or group private, right-click it in your contacts list, and select Mark as > Private