[Risolto] Custom field is not showing in WPML settings

I have a general question about custom fields. I manually made product fields by this function:

// Custom Product Price Per 2
woocommerce_wp_text_input(
array(
'id' => '_custom_product_price_per_2',
'label' => __('Prijs per 2 (€)', 'woocommerce'),
'desc_tip' => 'false'
)
);

And I save them also ofcourse with another function