how do I mark drum kits within a general patch bank in a rgd file?

Hi,
I'm currently working on some rgd files for some older synths that I
own for which there are no or only incomplete rgd files already present
in Rosegarden.

Right now I'm working on the rgd file for the Yamaha TG500, which has
multiple sound banks (each with 64 patches) and within these soundbanks
always the last patch (nr. 63) is a drumkit.

How do I specify within the rgd file that only a specific patch inside a
soundbank is a drum kit?

Thanks in advance for any help,
Arne