I figured it out, mycred uses an array for value in metakey mycred_reward,
I hooked the save_post action, but still don’t known how to get the value for the custom field I have created in the WC frontend form.
Here is my snippet code for the action, I put ?? where need any clue to get the value entered in form.
add_action(‘save_post’, ‘guarda_post’);
function guarda_post($post_id)
{
if(get_post_type($post_id) != “product”) return;
$meta_value = get_post_meta($post_id, ‘wcv_custom_product_mycred_reward’, true);
echo ‘That is the old value:’ . $meta_value;
$meta_value = ??
echo ‘Thit is the new value entered in WC Vendors Frontend form:’ . $meta_value;
}