Add notice when order is no longer editable.

Closes #6298

assets/css/admin.less

@@ -711,6 +711,11 @@ ul.wc_coupon_list_block {
 	.amount {
 		white-space: nowrap;
 	}
+	.add-items {
+		.description {
+			margin-right: 10px;
+		}
+	}
 }
 .woocommerce_order_items_wrapper {
 	margin: 0;

includes/admin/meta-boxes/views/html-order-items.php

@@ -214,6 +214,8 @@ if ( 'yes' == get_option( 'woocommerce_calc_taxes' ) ) {
 	<p class="add-items">
 		<?php if ( $order->is_editable() ) : ?>
 			<button type="button" class="button add-line-item"><?php _e( 'Add line item(s)', 'woocommerce' ); ?></button>
+		<?php else : ?>
+			<span class="description tips" data-tip="<?php esc_attr_e( 'To edit this order change the status back to "Pending"', 'woocommerce' ); ?>"><?php _e( 'This order has been paid for and is no longer editable', 'woocommerce' ); ?></span>
 		<?php endif; ?>
 		<?php if ( 'yes' == get_option( 'woocommerce_calc_taxes' ) && $order->is_editable() ) : ?>
 			<button type="button" class="button add-order-tax"><?php _e( 'Add Tax', 'woocommerce' ); ?></button>

readme.txt

@@ -136,6 +136,7 @@ Yes you can! Join in on our [GitHub repository](http://github.com/woothemes/wooc
 * Fix - Totals in taxes by date report.
 * Tweak - Improved headers sent notice to include file and line.
 * Tweak - When updating order status, ensure its a valid WC order status.
+* Tweak - Add notice when order is no longer editable.
 * Dev - Allow getting rating count for a specific rating value #6284.
 * Localisation - Nepal States.
 * Localisation - Mexico states.