In Yuri's Revenge, you can copy map entries from missionsmd.pkt and use them in your own PKT file for new game mode filters.

Example:
yuri.pkt

[MultiMaps]
1=XMP02T2
.........;cut down the list
8=TurfWar


[TurfWar]
Description=NAME:TurfWar
CD=2
MinPlayers=2
MaxPlayers=4
GameMode=urban

[JR007]

I believe you are posting a trick i was using hehe. was how i was planning to filter the maps out a lot more then normal..