Use the append technique to attach fields to transparent tables and structures.
To do so enter the name of the table or structure that you want to modify on the initial screen of the ABAP Dictionary. The remainder of this procedure is described in the sectionAttaching Append Structures in the ABAP Dictionary documentation.
Append structures can also be created in the ABAP Dictionary in display mode. In this case, no key from the SAP Service System is necessary.