Rated 5 out of 5 stars

Από τον/την ths στις Νοέμ. 4, 2019 · μόνιμος σύνδεσμος

I was able to move my Message Notes to XNote++, another note extension for Thunderbird that also works for TB 68 and higher.
You need to locate your messagenotesplus.sqlite in the TB profile folder to extract the notes. I can add technical details of the conversion if someone is interested.