How can I put bookmarks in a folder in the Opera browser (please read description)?

When I press F4 a small toolbar appears along the left hand side. There, I can click the "bookmarks" button and customize bookmarks (eg put them into folders etc). I made a new folder and placed 3 bookmarks into it, but for some reason its not in that folder structure in the actual bookmarks toolbar. I want to reduce the space I'm using by placing similar type bookmarks into certain folders. How can I do this?