The Help in a Help DOR takes priority over the Help in the application DOR, but for ROM applications it is not necessary to use a separate DOR. The use of the Help DOR is mainly in providing Help for internal applications or applications in other ROM cards.
If you intend to provide Help for an internal application you will need to provide all the same command codes for the commands. Therefore, it will be necessary to examine the structure of the internal application carefully.
This is readily achieved by opening the application with GN_Opf and A = OP_DOR to get a DOR handle, and reading the addresses of the Help structures out of the Help record.
The application name can be retrieved by letting FILER provide the filename: try listing all application names with the ":ROM.*//*" wildcard.