While exporting Firefox Bookmarks default file name is not proper, must be "Firefox_Bookmarks_Date"
Currently showing just "Bookmarks", later cant conclude of which browser bookmarks as we have many browsers.
Also ONLY FIREFOX has 2 formats of bookmarks saving, one is "Backup" in json format and exporting in HTML format, confusing end users.
The "bookmarks.html" format is ancient and cross-browser compatible. It's a good idea to add more information into the file name.
The JSON format retains more information but is proprietary to Firefox. Perhaps there should be a "Help" link on that menu to explain that.