Bookmarks are stored in a SESSION variable, so they go poof when you restart Zope or your browser.
The name of a bookmark defaults to the Id of the object, but you can edit it. If you make the name blank, you delete the bookmark.
You can download the current bookmark set as a text file from the bookmark management screen. You can upload such a file to re-create the bookmarks.
File objects with a content-type that starts with "text/" have a bookmark folder icon next to their bookmark icon. Using this, you can save or load bookmarks from the File object.
To install, download the latest release and unpack it into the Products directory of your Zope. Restart Zope, and you're done.