Rated 4 out of 5 stars

per Alexander Ihrig el mar. 20, 2021 · enllaç permanent

The collapse feature will be incorporated in my "Quote Colors" extension from up Version 3.0a6:
https://addons.thunderbird.net/de/thunderbird/addon/quotecolors/

Development is reported here:
https://www.thunderbird-mail.de/forum/thread/86842-quotecolors-update-f%C3%BCr-thunderbird-91/