Try opening the new Mailing List (double-click) and then adding the problematic Contacts by typing. It will auto-fill after a few letters, so you don't have to type very much. After doing this, close and re-open Thunderbird to see if your changes have "taken".

I am thinking that the Address Book is a bit troubled at the moment. I have been trying to move Contacts from one address book to another. The only obvious method provided is to drag-and-drop and it hasn't been working. I guess I should try in Safe Mode just to check if any add-ons are interfering.

Unfortunately, autofill doesn't work for me. That's because I've disabled it (because I dislike it).

Well, if this is a feature that's under development, I could make a lot of suggestions for making it better. For example, if you could copy a contact and paste it into the list group, that would be a good substitute for a malfunctioining drag and drop. But you can't even do something as basic as copy/paste.

Please tell me there's some other way to make a list group!

Oh, I think I just figured it out!

First, I thought maybe I should restart Thunderbird, to see if that might make the missing names show up. In fact, it had the opposite effect, and erased all the names, whatever few were showing up.

So that made me think there must be more to the process than just dragging and dropping.

So then, I selected all the contacts for the list, and drag/dropped into the list. Some names appear to be transferred and others don't. Or in some cases, none of the names were transferred.

Next, right-click on the mailing list folder and choose Properties. That will open a dialog, which shows all the contacts, even though they were not all showing before. Then click OK on that dialog. And now, all the contacts are showing in the mailing list.

I've closed and re-opened Thunderbird, and the names still show up in the lists. So I think they are there for good.

So now I'll continue with my other groups/lists, and I'll post again, if I learn any new info.

Hhm, but I do have another question.

One of my groups/lists is "family" where I have all my family names and addresses. If I delete them from the Personal Address Book, will that delete them from the family list too?

What I want is the family addresses by themselves, so that the address book that I use day to day is only my work contacts. But making the family list/group did not remove them from the Personal Address Book.

Does this mean I need to make another group/list, with all my work contacts? Or if I delete all the family contacts from the Personal Address Book, will they still remain in the family list?

Thanks :-)

A Mailing List is a subset of its parent address book. So a Mailing List inside Personal Address Book (PAB) can only hold Contacts found in PAB. So, no, you can't delete from PAB and still have them in a Mailing List. If you add a Contact (who isn't in PAB) to this Mailing List then Thunderbird will create an entry in PAB.

A Mailing List is a convenience to allow you to address an email message to many folk with a single entry. It isn't an address book per se.

But you can create as many address books as you wish. I have several. One shared via Google Contacts so its contents are accessible on my tablet. One general for work which doesn't need to be shared. Others for work which are specific to certain projects, clients or suppliers. Another just for friends' phone numbers which is shared with my phone. I do use Mailing Lists at work for certain subsets of colleagues.

I suggest you create a Family address book. Anything you add to the Address Book will land in PAB so you have to make a habit of foraging in it and moving Contacts out to their proper address books. Also keep an eye on Collected Addresses, as (by default, but you can change it) anyone you send an email message to who isn't already known to your Address Book will be copied there.

Yes there is some duplication, but I can share address books yet I cannot share Mailing Lists. Seems the best way to use what is available.

Autofill is cool. You make the computer do the work, rather than looking through lists yourself. Why search by eye when you have a computer there to do it for you, and will do it far more efficiently than you can?

Thanks for everyone's help!

The solution came from 2 different posts. One was my own post, where I figured out how to make mailing lists. And the other was from Zenos.