5.1 version (by Kaosmos) Rated 5 out of 5 stars

The latest version of my fork (5.1) has an option to collect addresses, even if they're already present in other addressbooks.

You can find it at https://nic-nac-project.org/~kaosmos/index-en.html#eac

Rated 5 out of 5 stars

You can find a version that should be fully compatible with newer versions of Thunderbird, modifed by me, at this address --> https://nic-nac-project.org/~kaosmos/index-en.html#eac