The addressbook is part of Thunderbird. It may take time to adjust to it, and you may enjoy using the contact list (press F9 or click View>ContactSitebar in compose window).

What aspect of the new address book is a problem for you?

Thank you Wayne [I am not happy with the new address book and its grey on paler gray lists etc., I don't seem to be able to do anything with it] But for now what I want urgently is to transfer selected names from the address book onto a fresh list. I am organizing some people to go to London on 21st April to protest the lack of action on climate change. Or Is it possible to revert to a former version of Address Book ? Sarah Lasenby

The previous format for the address book is gone.

Drag and drop should still work for you in the new release.

If you prefer the "old" table list of contacts display, you can do so.