how do i modify the query ad schema of a dataset job

Working with workbench 4 to pull data from a Progress database via an ODBC connection.  Want to modify the Query and Schema section to include additional fields and modify an exisiting field.  The existing field is an array that needs to be expanded into 6 different parts.  I do not want to recreat this job since there are hundres of destination column names that I've already added.  How do I do this?