"doc_id" Data Element Doesn't exist in UDesigner

For maintaining a proper Document Management System in Unifier, we have the following elements:

Apart from these fields, we need "doc_id" field in UDesigner which contains a unique value for each published document.

Right Now, we are able to get doc_id data on DataBase level as shown below:

unifier_dm_file table is picked from Unifier ER Views as shown below:

In our case, Most of the workflows will be having an attached document. so we would like to track this doc_id element within the business process form.

Is there any way to make it possible?