This allows you to add lots of contacts at once, from across multiple address books.
Tap “Import” on the contacts page, then select “Contacts Checklist” to see a list of all the contacts on your device. Set a check mark against all the ones you want to add.
If a contact has more than one email address, they will each be shown.
Addresses already included will not have a checkmark. (They are displayed so you can see if a contact already has an alternate address included.)