@Sylari I could force the page into the menu, but I personally don't like that approach. Some people may not want Magic Preview in their blog's menu, and if it's forced in, there's no user-friendly way to get rid of it. (One has to change the plug-ins code or hide the menu item with CSS.)
If I'm reading you correctly, you just figured out the URL on your own by guessing? Impressive! The URL is mentioned in the plug-in's documentation, but it's easy to miss. Maybe the documentation will be more prominent some day.