在Codeigniter中覆盖配置值

I have a custom config file in CI, loaded in autoload.php :

defined('BASEPATH') OR exit('No direct script access allowed');

$config['ci_bootstrap'] = array(

    // Menu items
    'menu' => array(
        'home' => array(
            'name'      => 'Home',
            'url'       => 'employees',
        ),
        'login' => array(
            'name'      => 'Login',
            'url'       => 'employees/login',
        ),
    ),

    // Sidebar Menu logged in
    's_menu_logged' => array(
        'dashboard' => array(
            'name'      => 'Dashboard',
            'url'       => 'employees/dashboard',
            'icon'      => 'fa fa-tachometer',
        ),
        'logout' => array(
            'name'      => 'Logout',
            'url'       => 'employees/logout',
            'icon'      => 'fa fa-power-off',
        ),
    ),

    // Login page
    'login_url' => 'employees/login',

    // Restricted pages
    'page_auth' => array(
    ),

);

In some pages I need to override some of the items, so I created another custom config file with some different values and loaded in controller :

$this->config->load('another_ci_bootstrap');

The changes didn't seem to take effect. Is it possible to do it in the above described way? I have searched this forum with similar QA's but didn't find a solution. The suggested possible duplicate post didn't resolve my problem. It's a multidimensional array!