I know how to make a single game one. I just don't want to keep adding the names on the mame64 -listxml command.

mame64 -listxml dkong > custom.xml

I don't know anything about MameDBGen tool. I will try this out. http://r0man0.free.fr/

Windows 10 Pro 64-bit / Intel Core i5-4460 3.20 GHz / 8.00 GB RAM / AMD Radeon R9 200 Series