i could be totally off base on this one and if i am i hope someone catches it, but if the top bar behaves like bottom bar it should be drag and drop onto the bar itself. i know thats the easiest way to add to the panel, or you might need to add the original file to the panel and delete the desktop icons afterwards. just a lil food for thought. hope it helps^_^
Ian, how you can see on the image, I added the Show Desktop Widget, but when I right click it there is no option “Show Desktop Settings” there is just: