I am currently using WebFX's XTree as the vertical menu for my accounting system: lots of different pages to go to, organized by functional area, with some submenus in most areas. This menu expands and contracts and, most importantly, stays open so I can see all items if choose to (helpful for comparing similarly-named items and figuring out which to click on).

What it does not do is anything other than navigate to a new page on click so that you have to reload the entire page, headings, decoration, menu tree and all. I want to, instead,