The Bookmark widget already uses the browsers local storage to save the bookmarks added to the clients machine. But no there is no export and import ability that you can manually trigger. But the next time you open your WAB app on that same machine then the bookmarks you added will be available.
I am in a situation where many of the main users of our WebMap sit at multiple different computers throughout their shifts. Not always the same machine.
When I add a custom bookmark, in what folder does the file reside on the local drive?
