Move the coupon field before subtotal on check if using WooCommerce on your child site.
Snippet Type
Execute on Child Sites
Snippet
remove_action( 'woocommerce_before_checkout_form', 'woocommerce_checkout_coupon_form', 10 );
add_action( 'woocommerce_review_order_after_cart_contents', 'woocommerce_checkout_coupon_form_custom' );
function woocommerce_checkout_coupon_form_custom() {
echo '<tr class="coupon-form"><td colspan="2">';
wc_get_template(
'checkout/form-coupon.php',
array(
'checkout' => WC()->checkout(),
)
);
echo '</tr></td>';
}