Here's an idea that may work for you:

Use address books to maintain your organization addresses, instead of doing it directly within the filters. You can create a separate address book for each organization you want to filter. Then for each destination folder you can have one filter (with no more than one or two entries!) which will simply check for addresses in a specific address book.

Address books should prove much easier to maintain than filters.

Thanks for the suggestion, Dominion. I may try that if all else fails. However, if an easy way of maintaining filters is available, I would prefer to use them. I don't really want to maintain separate address books. Poking an email address into a filter field, on the surface seems much easier - of course then, there remains my problem - Thanks again :-)

yes there is an easy way, two that I would use.

Instead of "address is" I would use "address contains" and the domain name rather than a complete email address. That way all mail for Anyone@domain.com will be caught. Almost no maintenance required.

The second Dominion already gave you.

From is in my address book and the address book name is specified. Address list maintenance in the address book is fairly simple. You retain your address granularity and your address book is actually useful as these folk are in it.

Conversion of your existing filter is sort of possible with only a little messing about. open the msgfilterrules.dat file for the account in notepad and copy the contents to of the relevant rule to a spread sheet and make it into a CSV file of addresses for import as an address book.

I thought about mentioning the partial addresses approach; but it doesn't work for non-corporate organizations whose members all have addresses in different domains. The address book should work for most everyone.

I can sort of understand why one might hesitate to use the address book approach. At the very least, it means setting up a new organization filter will involve dealing with two interfaces (filters and address book) rather than just one. A few extra steps, but bother accumulates.

On the other hand, moweaver, it does offer a way for you to have all the control you want over your filters. That being the case, I suspect that trying to maintain large lists of organizational email addresses within the filters themselves would fall in the "you're doing it wrong!" column. Like using pliers to tighten a bolt; yes, it sort of works, but only recommended when you don't have a spanner that fits the bolt in your toolbox.

If it helps, you need not think of the address books you create for use with filters as "separate address books". They're basically the same as the "lists" that the address book lets you create as a way of sending mails to many people at once. You can continue organizing all your contacts in your main address book, and just add the names and addresses you want to filter to the special-purpose book.

... If I were to suggest an improvement to how Thunderbird handles filters for multiple addresses, it would be this: make it possible for filters to interact with address book "lists" instead of entire address books. That would allow users to keep all their address book information in one place, and it would make "lists" more useful than they currently are.

make it possible for filters to interact with address book "lists" instead of entire address books.

filed a bug for that? Please do. The new Thunderbird address book "ensemble is the project name" is coming along. So a bug of that nature would perhaps be timely, given there is work on the bug to allow filters on send items being done.

Matt said

filed a bug for that? Please do.

It was just something that occurred to me as I was chiming in here. But you're right, I should probably do that. It would certainly be a sensible change to make.

(EDIT) It appears that the bug already exists:

Bug 180013 - have local mailing lists show up in "filter by addressbook" AB picker

There's a workaround mentioned down near the bottom, but adding this capability as standard functionality seems like a no-brainer.

Thanks for the suggestions, folks. While the domain approach would obviously work for some folks, my main interest is for a non-profit org whose members email addresses have disparate domains.

I like the "address list" approach. Since I have access to the membership roster for the org, it make sense in the near term to filter that way.

That said, I look forward to seeing where this "ensemble" work goes.

Thanks again for all the good suggestions.