Oh, I got an idea. Just add somethink like a bookmark manager, with the possibility to import/export bookmarks, analogous to the ZMI's import/export functionality with .zexp files. Importing this file would cause zope to resend the cookies, making it possible to transfer the whole bunch to other browsers.
Addendum: Make the bookmark manager folderish and let users store these files with a custom id/title into the bookmark manager. That way users can group bookmarks themselves and decide how they want to do it. And they can change to another set of bookmarks with a mouseclick. As these bookmarks are in no way security relevant and it's debatable if they really should be tied to users, I think it makes no sense to consider bringing a user folder into the game. cheers, oliver