I’ve created a custom field and that CF have a lot of data, something around 170 items. So, when I need to add a new CF and the update button is clicked nothing is saved, the load icon never desappear.
My question is: it is possible to create a query that does not necessarily need to go through all the fields and save them again,
to save only the new indexes or the ones that have changed?
No, it is not possible to cause ACF to only update changed values. ACF has no way of knowing what values have been changed and what values have not without attempting to update the values submitted.