How to add new menu entries to the MainWP Dashboard navigation

add_filter( 'mainwp_main_menu', 'mycustom_mainwp_main_menu', 10, 1 );
function mycustom_mainwp_main_menu( $left_menu ) {
    // Position of the menu item (0 = first, 1 = second, etc.)
    $index = 2;
    $sub_menu_after = array_splice( $left_menu['leftbar'], $index );

    $addition_item = array();

    $addition_item[] = 'Updates';                    // Menu item title
    $addition_item[] = 'custom_updates';             // Unique menu key
    $addition_item[] = 'admin.php?page=UpdatesManage'; // URL or page slug
    $addition_item[] = 'updates_custom_id';          // HTML ID attribute
    $addition_item[] = '<i class="sync icon"></i>';  // Icon HTML (optional)

    // Add the item to the leftbar array
    $left_menu['leftbar'][] = $addition_item;

    // Merge arrays to maintain menu order
    $left_menu['leftbar'] = array_merge( $left_menu['leftbar'], $sub_menu_after );

    return $left_menu;
}