A vendor may have additional related contacts whose details you wish to store against the "parent" record. For example, if the vendor is not available then a partner or spouse may be the preferred secondary contact.
Add a new contact
On the main vendor overview screen, additional contacts are listed under the main contact details on the right-hand pane. You can either click Add to add additional contacts, or click an existing contact to edit or delete them.
Modify an existing contact
To update an existing contact's details, click that contact's name in the Additional Contacts section. This will show that contact's details, and you can then choose to either Update or Delete via the Options menu.
As with deleting other records in the system, this may be not be available due to your user role, or its deletion may be denied if the record has a history.