I support this idea and one thing is also seems to be essential - when you search for a bookmark, let it folder path be displayed in adjacent column or in hint balloon maybe.
Why this can be very useful is because I have had so many times when managing bookmarks the intended click on the bookmark or worse, on the folder is registered as click and hold and this item is instantly moved to some closest, almost random, unrelated folder.
Having the extensive folder structure makes discovering where a whole folder is gone a great pain in nether regions.
The only viable option up to date is to export/backup all bookmarks and search for the name in the resulting file.