I have just had to reinstall Avast Anti Virus (Free) and have lost all my bookmarks…Being unable to retrieve my Old Bookmarks definitely prohibits me from purchasing the full version…Maybe u can create a save bookmarks folder for Documents or some such folder on the C: drive…
I use avast free 17.5.xxxx and Firefox as my primary browser on all three systems and I have never lost bookmarks if a reinstall or clean install has been done.
I can only assume that you are talking about the SafeZone Browser ?
If so it is possible, open the AvastUI > Settings > Components - now click on the ? top right of the screen (context menu help) > Security components overview - scroll down to the SafeZone Browser and click the Read more… link. Now you have a list of options - including - How do I import bookmarks from the previous SafeZone or from other browsers? - open that.
It’s easy enough to save and import the bookmarks from a prior version of SafeZone.
If you do a clean install, you will have to rebuild the items in the Bookmarks Bar.