Hide Pages

new-role.php

register_activation_hook( __FILE__, 'my_initial_setup' );
function my_initial_setup() {
    $admin = get_role( 'administrator' );
    $overlord_caps = $admin->capabilities;
    $overlord_caps[] = 'be_overlord';
    $role = add_role( 'overlord', 'Overlord', $overlord_caps );
}

page-category.php

add_action( 'init', 'ny_page_category' );
function ny_page_category() {
	
	$show_ui = ( current_user_can( 'be_overlord' ) ) ? true : false;

	$labels = array(
		'name'              => 'Page Categories',
		'singular_name'     => 'Page Category',
		'search_items'      => 'Search Page Categories',
		'all_items'         => 'All Page Categories',
		'parent_item'       => 'Parent Page Category',
		'parent_item_colon' => 'Parent Page Category:',
		'edit_item'         => 'Edit Page Category',
		'update_item'       => 'Update Page Category',
		'add_new_item'      => 'Add New Page Category',
		'new_item_name'     => 'New Page Category Name',
		'menu_name'         => 'Page Categories',
	);
	$args = array(
		'hierarchical'      => true,
		'labels'            => $labels,
		'show_ui'           => $show_ui,
		'query_var'         => true,
		'rewrite'           => array( 'slug' => 'page_category' ),
	);
	register_taxonomy( 'page_category', array( 'page' ), $args );
}

pre-get-posts.php

add_action( 'pre_get_posts', 'my_hide_system_pages' );
function my_hide_system_pages( $query ) {
   if( is_admin() && !empty( $_GET['post_type'] ) && $_GET['post_type'] == 'page' && $query->query['post_type'] == 'page' && !current_user_can( 'be_overlord' ) ) {
       $query->set( 'tax_query', array(array(
           'taxonomy' => 'page_category',
           'field' => 'slug',
           'terms' => array( 'system-page' ),
           'operator' => 'NOT IN'
       )));
   }
}