WordPress Dashboard. Order by Page Template

functions.php

<?php /**
 * 
 * Adds a Column to WordPress pages admin so you can easily see
 * which pages are using which page template.
 * 
 * @since 1.0
 */
function la_modify_page_table ( $columns ) {

  /* Add a Page Template Column */

	$custom_columns = array(
		'template' => __('Page Template', 'wordpress')
	);

	$columns = array_merge( $columns, $custom_columns );

	unset($columns['comments']);

	return $columns;
}

add_filter('manage_pages_columns', 'la_modify_page_table');

/**
 * Register our column as sortable
 */
function la_sortable_template_column($columns) {
	return array_merge( $columns, array( 'template' => 'template' ) );
}

add_filter('manage_edit-page_sortable_columns', 'la_sortable_template_column');

/**
 * 
 * Templ
 */
function la_template_column_orderby( $query ) {

	if (!is_admin()) return;

	$orderby = $query->get('orderby');

	if ( $orderby == 'template' ) {
		$query->set('meta_key', '_wp_page_template');
		$query->set('orderby', 'meta_value');
	}
}

add_action('pre_get_posts', 'la_template_column_orderby');

/**
 * 
 * The content for our template column
 * 
 * 
 */
function la_modify_page_table_content( $column_name, $post_id ) {

	/* Available Page Templates */
	$templates = get_page_templates();

	/* Template used on this page */
	$current_template = get_page_template_slug($post_id);

	foreach ($templates as $label => $filename ) {
		if ($filename == $current_template) {
			echo "$label / $filename";
			return;
		}
	}

	echo 'Default';
}

add_filter('manage_pages_custom_column', 'la_modify_page_table_content', 10, 2 );