The bookmarks are stored in "Local Storage" which is a tiny (5MB max) database that is part of your browser.
There's no easy way to share them. I tried renaming one in developer mode but it did not work.
We need a widget that keeps bookmarks and sessions in a shared database, so that you could back them up and give them to other users and see them on different devices... if you find a widget like that you should post about it here.
I checked the source for the Experience Builder Bookmark widget and it's still using Local Storage, so the problem will not go away if you switch from WAB to EXB.
When local storage fills up these widgets simply stop saving. I hit the problem a few weeks ago when I tried to save a session and nothing happened. When storage is full, there is no error or warning message. Since the 5MB is the total storage shared across all apps in your browser, it could be some totally unrelated app has filled up the storage, so there might not be any way to clear it out other than using the developer tools.
