Set the order of the pages/posts in the admin section according to the last modified/editing date

set_default_post_type_order_in_admin_area.php

//* @ Method 1
// Set the order of the pages/posts in the admin section descending according to the editing date [for all post/page type] 
function orderby_modified_posts( $query ) {
    if( is_admin() ) {
  		$query->set( 'orderby', 'modified' );
        $query->set( 'order', 'desc' );
    }
}
add_action( 'pre_get_posts', 'orderby_modified_posts' );

/* @ Method 2

// Set the order of the pages/posts in the admin section descending according to the editing date [for specific page type] 
function orderby_modified_posts( $query ) {
    if( is_admin() and isset($_GET['post_type']) and $_GET['post_type'] === 'page') {
  		$query->set( 'orderby', 'modified' );
        $query->set( 'order', 'asc' );
    }
}
add_action( 'pre_get_posts', 'orderby_modified_posts' ); 

*/