KevinTheJedi
I'ts solved! I'm gonna post the code because tookme a lot of time finde the right variables:
You might look in the database for the righ ID for the custom field using a query like:
SELECT id, name, label FROM ost_form_field WHERE name IN ('xxx');
In this case xxx is the field variable, but you can pick any of the fields, more than once.
Then in the include/class.queue.php line 599 aprox, copy an existing field and update to match your own using the results from the above query.
And wala! The field has been exported.
I hope this gonna be useful for others.
