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 gContactSync by adsrfvfgA
Rated 4 out of 5 stars
Excellent and very easy to use add-on. But latest version 3.2.0 is not compatible with Firefox 78.11.0.
Hope and wish it gets evolved, for now I'm temporarily using with success alternative add-on Google-4-TbSync:
https://addons.thunderbird.net/en-US/thunderbird/addon/google-4-tbsync/
To create your own collections, you must have a Mozilla Add-ons account.