When one hits the "More Settings..." button of the panel configuration panel (the place from which one can edit the panel), one gets the menu with alignment, visibility and so on. As this menu is positioned just above the panel, it hides the "More Settings..." button (in English a small part of it is still visible, but this may not be the case in all languages). The only way of closing it is by clicking on the desktop or another window, which in turn closes the panel configuration panel. I think the popup menu should be closed when clicking anywhere outside of it, like any regular popup. Reproducible: Always I'm using Project Neon daily ppa.
*** This bug has been marked as a duplicate of bug 334970 ***