Claws already allows using vcf address books. In my case, I have a vcf book with all my addresses and it works fine for sending emails. However, I want to make a filtering rule for if the email is coming from one of my contacts in that book. But it only allows "regular" address books, not vcf books. Please consider allowing vcf books for filter rules.
I just noticed that vcf address books are also not allowed in the criteria for bogofilter, perhaps a new bug report should be opened? Specifically, "Whitelist senders found in address book/folder".