you will have to build small workflow which

- will go through all the items in the list (that still have empty new column)

- then for every single item found, read (hidden) FormData column (XML structure)

- parse that XML out for respective control name/guid and its value

- update new list column with that value

Thanks for the quick and (it seems) accurate answer, I'll try it.

Thanks it works fine, just a last question, the control that contains the value to retrieve is a DropDownList control, how to retrieve the text attribute (xml structure), because by default we get the value of the attribute (in a ddl its ID)?

so is original form control a lookup to another list?

yes it's a lookup to another list!

then I would suggets you make new list column of lookup type as well.

in that case ID you read out of FormData is correct value to write into that columns.

otherwise you will keep in your list just a static text that will not get updated once you change text column in referenced list.

if you insist to copy over text column from referenced list, you have to use query list action and by the ID value from FormData you have query for respective text column value and write that value to the list

As it's a list for traceability of information, I choose the second option . Thank you for your support