On the menu in the bottom right (≡), you have options for “Backup” and “Load contents”:
TabFern collects window and tab titles, URLs, and favicon URLs in order to do what it is supposed to do! All information is stored only locally, on your computer. The TabFern extension does not send any data to any party.
Google may collect information when you install or uninstall TabFern, but TabFern itself does not report those activities or otherwise collect data about usage. If you like TabFern, please star it on GitHub (Link Below)