You can re order admin left menu by below code:
/*
* Code below groups Dashboard/Posts/Pages/Comments together at the top of the dashboard menu.
* If you were to have a custom type that you want to add to the group use the following edit.php?post_type=YOURPOSTTYPENAME
*/
function reorder_my_admin_menu( $__return_true ) {
return array(
'index.php', // Dashboard
'edit.php?post_type=page', // Pages
'edit.php', // Posts
'upload.php', // Media
'themes.php', // Appearance
'separator1', // --Space--
'edit-comments.php', // Comments
'users.php', // Users
'separator2', // --Space--
'plugins.php', // Plugins
'tools.php', // Tools
'options-general.php', // Settings
);
}
add_filter( 'custom_menu_order', 'reorder_my_admin_menu' );
add_filter( 'menu_order', 'reorder_my_admin_menu' );
Above code used custom_menu_order and menu_order hook to re order existing menu items. Hope this help you well!