Switchvox - How to edit and delete contacts from Digium phone's Contacts application

Q: On my Digium phone used with Asterisk, I added contacts from the phone's Contacts application. How do I edit or delete those contacts?

A: The current Digium phone firmware (for Digium D40, D50, and D70) permits adding contacts from the phone's Contacts application, but does not permit editing and deleting contacts. There is an existing request to provide this capability.

However, see also the answer to the following, related question in the Sangoma Phones + Asterisk FAQ in the Asterisk Wiki:

Q: Is it possible to add contacts from the phone and have them stored on Asterisk?