Orders as the first submenu item on the WooCommerce WP-Admin menu

woocommerce_nav_admin_orders_first.php

<?php
add_filter( 'custom_menu_order', 'woocommerce_nav_admin_orders_first' );
function woocommerce_nav_admin_orders_first( $menu_order ) {
	if ( is_admin() ) {
		global $submenu;
		if ( isset( $submenu['woocommerce'] ) && is_array( $submenu['woocommerce'] ) ) {
			$temp = array();
			//Add orders as first
			foreach ( $submenu['woocommerce'] as $submenu_item ) {
				if ( isset( $submenu_item[2] ) && $submenu_item[2] == 'edit.php?post_type=shop_order' ) {
					$temp[] = $submenu_item;
					break;
				}
			}
			//Add the remaining items
			foreach ( $submenu['woocommerce'] as $submenu_item ) {
				if ( isset( $submenu_item[2] ) && $submenu_item[2] != 'edit.php?post_type=shop_order' ) {
					$temp[] = $submenu_item;
				}
			}
			$submenu['woocommerce'] = $temp;
		}
	}
	//We didn't touch the $menu_order variable at all, we just needed to have somewhere to hook into and then 
	return $menu_order;
}