The answer is, so far as I can tell, no. I've run into yet another problem, and that is that the menu items always expand to the right; so if your rightmost menu item opens into a second or third level, everything runs off the side of the screen. Again, if there's any way to change this nobody knows what it is. When we migrate to one of the new templates, we're going to use the one whose main menu is in the sidebar. That should avoid the problems.
Come to think of it, it might be possible to move the main menu to the sidebar; but I haven't thought that through.