Some actions are disabled in the top menu in error
Add local entries to your address book.
Intending to back up your address book, go to File > Save Address Book as vCard. Notice that "Save Address Book as vCard" is greyed out and cannot be selected.
"Save Address Book as vCard" being grayed out leads to confusion as users don't know how to activate it.
This issue was brought up in the Evolution mailing list and it was suggested that a bug report be made. The present solution is to right-click the address book entry in the left sidebar and select "Save as vCard...". Now File > Save Address Book as vCard is no longer greyed out.