To try the thousands of add-ons available here, download Mozilla Firefox, a fast, free way to surf the Web!
CloseWelcome to Firefox Add-ons.
Choose from thousands of extra features and styles to make Firefox your own.
CloseReview for FireTray by _Anne_
Rated 5 out of 5 stars
I found it: https://addons.mozilla.org/fr/firefox/addon/firetray/versions/0.6.0
It fixes the problem, and works great as before.
To create your own collections, you must have a Mozilla Add-ons account.