BuddyPress.org

Check out bp-core/bp-core-adminbar.php. The items in the admin bar are hooked to bp_adminbar_menus, and are ordered by the priority argument. So, for instance, if you want to put a button between the Blogs and Notifications menus, I’d write the button into a function called bp_adminbar_my_button, then use the hook add_action( 'bp_adminbar_menus', 'bp_adminbar_my_button', 7 );.