Yep, believe so. Try this (enqueue in admin styles):
Show sub-menus at all times
#adminmenu .wp-submenu,
.folded #adminmenu .wp-submenu {
display: block !important;
}
Hide Pop-up Navs
.wp-submenu.sub-open {
display: none !important;
}
That should get you started with it, otherwise you can go to wp-admin.dev.css and edit the navigation there, starting at line c. 1519. Hope that helps..