I am unclear on what you are asking. Here are the steps I always suggest, and most users report success, although it's easy to overlook details, which are important.

https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer

here is the info in brief steps:

1. ensure thunderbird is NOT running on old machine
2. enter %appdata% in search window on task bar and press Enter key
3. this should open windows file explorer in Appdata\roaming folder
4. highlight the Thunderbird folder and copy to external media
5. ensure thunderbird is installed on second computer, started once and NOT running
6. enter %appdata% in search window on task bar and press Enter key
7. you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it

#   start thunderbird and all should be there

Oh, a few things that need to be credited: The author reads,

1. Locate the master profile folder on the source computer as above. (Master profile? WHAT kind of profile, as is WHERE IS IT?)

5. On the source computer, copy the Thunderbird folders... (Should he just say THUNDERBIRD FOLDERS WHERE?)

6. The big one: On the destination computer, remove (or rename if you need a data backup or to preserve an old profile) any Thunderbird folders in the destination folders Windows(C:)/Users/~/AppData/Roaming and Windows(C:)/Users/~/AppData/Local directories.

Huh? It makes sense when he writes (kind of),

"On the destination computer, remove any Thunderbird folders in the destination folders Windows(C:)/Users/~/AppData/Roaming and Windows(C:)/Users/~/AppData/Local directories."

It seems as though you're DELETING Thunderbird folders, and planning to dub in YOUR OWN Thunderbird folders that you copied in the same place on the SOURCE computer

That's what I thought, but it DOESN'T WORK.

Was it because I used Thunderbird 145? Will it work if and ever I find version 144?

Thanks guy, if I know anyone will respond to this.

Hi there,

I should have put in it I had a stroke a couple of years ago. Frustrating!

Three points:

1) You're talking about " Appdata\roaming folder" but what about Appdata\LOCAL folder? Do we need to dub Thunderbird to the LOCAL folder as well as ROAMING?

2) Also, I get no answer dubbing it. No overwrite message.

3) And IF the original Profile on the DESTINATION computer is wrong, I get a message that Thunderbird WILL NOT WATCH. I get "Your Thunderbird profile cannot be loaded. It may be missing or inaccessible."

4) On installation, 145 continue to WATCH us work. I couldn't just not start it.

One thing that will help is be able to find HOW MANY PROFILES DOES THUNDERBIRD recognize? The date of the profile that makes sense?

Thanks. Your helping is helpful. (It's also using SOURCE destination (Windows 11) and DESTINATION computer (Windows 10). More clear.

The LOCAL is not necessary. Thunderbird can work with only one profile. It sometimes accumulates many, but they're just baggage. The inaccessible message happens if the desired profile and associated profiles.ini are not loaded together. The purpose of using the thunderbird folder and not the profile folder is that the thunderbird folder includes both. Here is what happens: thunderbird opens the profiles.ini but the profile it is identifying isn't there. That can be an easy fix, often by overtying in the profiles.ini the actual location. this is avoided when the thunderbird folder overwrites the default thunderbird folder. what often happens is the user pastes the transferred thunderbird folder to the appdata\roaming]\thunderbird folder which creates appdata\roaming\thunderbird\thunderbird - and that is why I state that a prompt to overwrite should happen.