An elegant way to enhance the default Univeral Theme menu behaviour is described in Maxime Tremblay's Blog:

By default, it's only possible to expend the side navigation menu children submenu by clicking on the corresponding down arrow.
Here's how you can do if you would like to be able to do the same thing by simply clicking on the list entry text.

I'm using Maxime's trick on this site (as you may have noticed), and it works like a charm.