wc-admin-view-thankyou-link.php

<?php // only copy if needed!


/**
 * Adds a link to view the "order received" page to the orders admin.
 * REQUIRES WC 3.0+
 *
 * @param \WC_Order $order the current order object
 */
function sv_wc_order_received_page_admin_link( $order ) {

	if ( $order instanceof WC_Order ) {

		$args = array(
			'order-received' => $order->get_id(),
			'key'            => $order->get_order_key(),
		);

		ob_start();
		?>
		<?php /* incorrect CSS class added here so it adopts styling we want */ ?>
		<p class="form-field form-field-wide wc-order-received wc-order-status">
			<label for="order_received">
				<?php esc_html_e( 'Order receipt:', 'my-textdomain' ); ?>
				<?php printf( '<a href="%s" target="_blank" rel="noopener">%s</a>',
					esc_url( add_query_arg( $args, wc_get_checkout_url() ) ),
					__( 'View thank you page &rarr;', 'my-textdomain' )
				); ?>
			</label>
		</p>
		<?php
		echo ob_get_clean();
	}
}
add_action( 'woocommerce_admin_order_data_after_order_details', 'sv_wc_order_received_page_admin_link', 1 );