Excuse me, I meant I now have 102.0.2 after several other downloads. And I still have not been able to get the Mail Merge App. It is bewildering! Thank you!

I don't understand the issue. Mailmerge works fine in 102, and is at release 9.0.5. Are you saying you are unable to dowload it? On the page color, you may have the dark theme installed. You can check that at Tools>addons>themes.

Dear David, so many thanks for this reply! I've survived with TB now for decades running a non-profit program.

    It's a love relationship with you and all the other folks who make it work. 
    And yet now over two weeks ago TB went crazy on me. I had 102.0.1 that was doing fine with Mail Merge/MM included in the pull down File menu.  
    For years I've communicated with my hundreds of supporters/donors for my scholarship program with disenfranchised Haitian children. Always able to address them by their first name.  
   And then all of a sudden MM disappeared from the File pull down menu. I began downloading the latest TB programs, probably 6! None of them had MM. Except now this last version 102.0.2 (64-bit) does have MM in the upper right hand screen. 
    BUT, click on that and I get this completely strange format of Excel which is empty and wants me to start MM totally anew!  I still have my dozen of MM lists! And I tried copying one to enter into this new Excel format.  Didn't work, it had each name, address and the single alfabet of the name making it impossible to create a new version. I'm at a total loss for using MM. In the File pull down menu there is still the function, "send unsent messages" but it is dead.  
    Hopefully you and I can continue to exchange the issues of this problem. Forget about the reverse color problem which I never asked for.  If we can get MM to come back!!!
    Many thanks again!    With best wishes!   Tom Luce

OOPS, I tried separating my thoughts and that doesn't work on this reply system! 1. It's a love relationship with you and all the other folks who make it work. 2. And yet now over two weeks ago TB went crazy on me. I had 102.0.1 that was doing fine with Mail Merge/MM included in the pull down File menu. 3. For years I've communicated with my hundreds of supporters/donors for my scholarship program with disenfranchised Haitian children. Always able to address them by their first name. 4. And then all of a sudden MM disappeared from the File pull down menu. I began downloading the latest TB programs, probably 6! None of them had MM. 5. Except now this last version 102.0.2 (64-bit) does have MM in the upper right hand screen. BUT, click on that and I get this completely strange format of Excel which is empty and wants me to start MM totally anew! I still have my dozen of MM lists! And I tried copying one to enter into this new Excel format. Didn't work, it had each name, address and the single alfabet of the name making it impossible to create a new version. 6. I'm at a total loss for using MM. In the File pull down menu there is still the function, "send unsent messages" but it is dead. 7. Hopefully you and I can continue to exchange the issues of this problem. 8. Forget about the reverse color problem which I never asked for. If we can get MM to come back!!! 9. Many thanks again! With best wishes! Tom Luce

This is an addon, and a major release, according to author. Another gentleman posted a problem with the addon, and it seemed similar to yours. I noticed that the 'details' tab in the addon does now list the documentation (which appears to be a bug in itself), so I suggest you file a notice with the author at https://addons.thunderbird.net/en-US/thunderbird/addon/mail-merge on your question, and it appears that full documentation is available at that site. Good luck to you and best wishes to you in supporting the Haitian children.

Dear David, many, many thanks for your latest reply! I couldn't reply to it from the email format. But I have signed into the AddOns site and am beginning to navigate there. I've downloaded their latest Mail Merge. We'll see whether that functions. I was able to change the color from black to white! So again, Thunderbird's loving community is helping me solve this terrible problem! Best wishes.