To manage your Bookmarks, left click on the star in the upper right corner to get to your bookmarks. By left clicking on a specific bookmark and keeping it depressed you can move the bookmark wherever you want. Right click in the bookmark window, and you can create a new folder. It took me a while but I figured it out.
As an alternative, you can also left click on the orange Firefox block, it will give two menus. The light blue one has a yellow star Bookmark selection, when you move the cursor over it the bookmark menu appears.
I hope this helps.