A Thunderbird launcher AutoIt script that automatically deals with those pesky multiple Master Password prompts.
Notice: The addons StartupMaster and Master Password+ mysteriously appear to be working again so this script may not be needed anymore.
Download and install AutoIt from here: https://www.autoitscript.com/site/autoit/downloads/, then download "Thunderbird Password Helper.au3" from this repo and place it somewhere convinent. If you have installed Thunderbird to somewhere other than: "C:\Program Files (x86)\Mozilla Thunderbird\thunderbird.exe", then please edit the path near the top of the script. (I might add automatic installation location detection in a later version.)
Run Thunderbird Password Helper.au3 and type in your Thunderbird Master Password into the box.
AutoIt 3 installed from here: https://www.autoitscript.com/site/autoit/downloads/
The script prompts for the master password, launches Thunderbird then types the password into each password prompt for you.
I (the author) ACCEPT NO RESPONSIBILITY FOR ANYTHING BAD THAT ARISES FROM USE OF THIS SCRIPT. USE WITH CAUTION! I quickly wrote this script due to the usual workaround addons not being compatible with Thunderbird 60 (Quantum). Bugs and security problems may be present. There is also a small chance the script could type the password into the wrong window.
Q: The script is just typing in infinite password boxes or has otherwise gone wrong! What do I do?
A: Right click on the AutoIt icon in the System Tray (bottom right of the screen) and click "Exit".
Q: Why do I still get the multiple password prompts after launching Thunderbird?
A: You need to run the script instead which prompts for the master password then launches Thunderbird by it's self.
Q: Why don't you provide a compiled version of the script that runs without needing to install Autoit?
A: Because some virus guards flag compiled AutoIt scripts as viruses.