In the selection of the default address book to put new contacts (when clicking on the person icon next to an email address/contact in the email view) in Settings -> Address Book it is only possible to select local address books but not any CardDAV address books.
In the selection of the default address book to put new contacts (when clicking on the person icon next to an email address/contact in the email view) in Settings -> Address Book it is only possible to select local address books but not any CardDAV address books.