Case Contacts
A case contact is a person or organization involved in a case that is not the client, adverse party, or family member/non-adverse party. This could be opposing counsel, a translator, a guardian ad litem, etc.
Site administrators can configure different ways to add a case contact, but there is often a "People" or similar tab that lists all existing case contacts. That list has "+" icon in the filter bar.
The built-in add case contact form initially displays a list of all people and organizations already added to the case (not just contacts), then an "Add Case Contact" section:
Not shown above is a "Create New Contact" button off to the right.
You should typically use the Search option to avoid creating duplicate contact records.
The Search option only searches for individual contacts not organization contacts.
The Create New Contact button (not shown) lets you create a new Contact record (in the system, not just for the case) and set the Case Contact Type for the new contact on the case.