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