You might want to consider downloading the Opera extension Add Bookmark,
https://addons.opera.com/en/extensions/details/add-bookmark/?display=en
as it makes taking a bookmark easier,including clicking on the star in the Address bar to add a book mark, and placing the bookmark in a folder -- all rather seamlessly done. You can also access that star in the context menu (right click on the web page), and get the same option on where to place the bookmark.