The two default address books, abook.sqlite and history.sqlite (Personal Address Book and Collected Addresses) can be copied to the new profile, overwriting the existing files. Others, such as abook-1.sqlite can be imported from Tools/Import.

The msgFilterRules.dat files can be copied to account subfolders of Mail and ImapMail.

Thanks! Can abook.sqlite and history.sqlite also be imported, while I'm at it?

Do the other existing address books have to be deleted from the laptop before importing the ones from the desktop, or will they overwrite what exists?

If you already have abook.sqlite and history.sqlite in the new profile, the ones from the old profile can be imported the same as other sqlite files. To be safe, rename e.g. abook.sqlite to abookOLD.sqlite before importing. Do the same with others to keep the new and old imports separate. Afterwards, books can be organized by drag and drop of contacts.

The problem with importing the sqlite files is that it asks which address book to import each one into.

And there are several new address books in the desktop that are not in the laptop.

I take it the address books are indexed somewhere, so that all the sqlite files can not just be copied over?

When you import a sqlite file, choose 'new directory' as in the picture, so a new address book is created in Address Book, in this example with the name abookOLD. You can only copy abook.sqlite and history.sqlite directly into the new profile, if you don't need the existing ones; the other sqlite files must be imported as shown.

So I guess the process will be, for each address book:

1. Import, say, abook-10.sqlite.
2. Figure out which of my existing address books it is.
3. Delete that existing book, if it already exists on the laptop.
4. Rename abook-10 to the name I just deleted, or didn't find.

Do you happen to know where the names of the address books are stored?

If you open Config. editor in Settings/General, and enter the address book name, e.g. testbook, in the search, you will find a preference ldap_2.servers.testbook.filename with the value of the name of the sqlite file, e.g. abook-2.sqlite.

An associated question:

Normally I use TB on my PC. When I travel, I want to move the address books and filters to the laptop. Then when I return, I want to move any that have changed back to the PC.

No accounts have been added since the TB installation was copied to the laptop.

So, if I understand this, abook.sqlite, history.sqlite and msgFilterRules.dat, if they have changed, can just be copied over.

For each changed abook-n.sqlite, if it does not correspond to the same address book on the source and destination computer, it has to be imported and renamed.

If it does correspond to the same address book on the source and destination computer, can it just be copied over, or does it also have to be imported and renamed?

The only books that can be copied over are abook.sqlite and history.sqlite. The others can only be transferred by importing.

To avoid having to transfer address books between devices, consider using a network source like Google Contacts that can be added as a CardDAV address book, and synced between all devices. Other providers can be synced the same way with the TbSync add-on.

Thanks!

What would happen if I only copied abook.sqlite and history.sqlite, and none of the other sqlite files?

If you just copy those two and overwrite the existing files, the Personal Address Book and Collected Addresses will be updated.

Then I'll simplify: Just copy abook.sqlite, history.sqlite and any changed msgFilterRules.dat files.

I use filters to sort incoming mail into folders. If I have a folder called Club, say, I make an address book Club and a filter that puts email addresses in that address book into the Club folder.

Not copying the other abooks only means that when I see a sender in Inbox who belongs in Club, I'll have to put their address into Club once on each computer.

I could also copy the entire Thunderbird directory from the PC to the laptop on leaving, and then copy it back on returning. Would that work?

If that's done once, then as long as no new address books are added, the abook-*.sqlite filenames would be the same for address books on both machines. But they would still have to be moved by importing, correct? Just that I would have a permanent list for which address book to import each one into.