Rated 4 out of 5 stars
Thank you very much for your efforts. I'll send you my French translation soon.
Only one negative note: QNote is in conflict with the extension QuickText (https://addons.thunderbird.net/thunderbird/addon/quicktext/) that I'm using too. I need to disable QNote if I want QuickText to be enabled when TB starts. But I don't know which extension is responsible...
This (hopefully) is fixed with 0.6.2