mmenu.js : Is adding support for accordion style collapsable/expandable menus possible?

From what I understand this isn't possible out of the box with mmenu or any plugin for it. What I need is an easy way to format the submenus so that they are clickable and collapse/expand, as is clear in the screenshot below. If I'm wrong on this and there are any examples of a plugin/css that will easily do this I'd love to know.

I've discovered that this is indeed possible, simply by adding the class "Vertical" to any child elements.