How to set Navbar to be a sidebar by default?
I found a way to do this in a very simple custom module without any hacking or patching to Navbar code.

Just create and enable a custom module that contains (assuming your module is called custom):

/**
 * Implements hook_navbar_breakpoints_alter().
 *
 * Nullifies the breakpoint that switches the navbar to horizontal orientation
 */

function custom_navbar_breakpoints_alter( &amp;$data ) {
    $data["wide"] = "not all";  
}


The navbar module defines a hook, hook_navbar_breakpoints_alter, using drupal_alter, that allows its hard-coded breakpoints to be overwritten. 

not all seems to me the cleanest and most intuitive way to implement an impossible media query condition (related: How to set a media query condition that is never met?).

This makes the switchable horizontal masthead view of the navbar menu, quite literally, the default on not any device.