default menu state

hemingweb

Is there a config option to set the default fuel menu to collapsed? and/or how could you specify which $config['nav'] options were open or collapsed?

almostcompletely

The display of public side menus is down to your CSS/JS.

The [li] for a fuel menu's active page is given a class of "active" when on that page. Again, it's down to your CSS & JS as to what to do with it.

hemingweb

I'm referring to the menu with fuel cms, on the left of the screen. not the menu generated by the navigation module

admin

There currently is not a setting to automatically collapse the left hand menus. However, you can leverage your own global javascript file to call the click event that is set on the id of the H3 for the toggler. To add your own global js file, add the following to your MY_fuel.php:
$config['fuel_javascript'][] = array('my_js');