Great question. Hope someone knows how.
I finally figured out how to delete the ones I didn't want, thanks to a post in another thread ... launch the bookmarked site, close it. Launch bookmarks again, go to the "history" tab and un-click the red star. That removes the site from the bookmarks list.
Otherwise, it seems my bookmarks list gets longer and longer whether or not I make a bookmark. It's a mystery to me.