Do you have any ideea how can be imported attachements with the Proposal using Interface Tables? I don't understand where is kept the folder number in the attachement folder from ITG. Is there any sequence/table for the folder number and for the attachements id?
as far as I know, there isn't any feature for attachments in the Open Interface API. But you can add an execution as first workflow step to import the attachments.
All you need to do is to insert a row in knta_documents an a second one in knta_references (pay attention on parameter2 which is the document_id). After Commit move the document to the appropriate sub directory in attachments directory on filesystem. The last two digits of the document_id are the name of the sub directory.
Just add an attachment manually, have a look at these tables and try to imitate the application. Don't forget to update entity_last_update_date on kcrt_requests.