I am trying to translate the custom fields labels with a .po/.mo file and everything works only if I use the PHP code to define the custom filed but only if I completely remove any definition of these fields from the builder. However, this does not happen with custom taxonomies for example for which I just put the PHP code in the theme and leave the taxonomy definitions in the builder as well. Is it possible to do the same with custom fields as well?
To translate custom field labels or taxonomy labels, you need to generate the PHP code and add it to the file functions.php and use a translation plugin to scan the text to translate.
You also need to delete them from the builder to avoid any potential issues. Please read more on the documentation https://docs.metabox.io/extensions/meta-box-builder/#getting-php-code
Oh yes, I know this and as I said it works well also with a .po/.mo file without any translations plugin.
I just wanted to know if it was possible to make the translation work without deleting the field definitions from the builder (as happens for custom taxonomy labels) but from your answer I understand that it is not possible. Thanks anyway.