This has been released: https://portableapps.com/news/2020-07-17--thunderbird-portable-68.10.0-r...
I've built a test version of the current stable Mozilla Thunderbird build with portablization of newer extensions and dual-mode 32-bit + 64-bit support. It's packaged in release form, so be sure to back up your existing install before testing.
Download REMOVED, this has been released
85MB download / 337MB installed
Please test out portability with extensions and calendars and report back your findings so I can push this out for everyone. Thanks for testing!