Depends on what exactly you want to achieve... but I guess look at the _Map classes...
I want to create groups of random enemies. right now when you set up random encounters. you create one group. lets say map id 5 has 5 enemies you can encounter upon walking every 30 steps. Thats means the core system picks from those 5 enemies, one troop for you to fight.
Thats fine.
I want MULTIPLE groups. I want to add a note tag that is like:
<enemy group 1>troop_id, troop_id</enemy group 1> <enemy group 2>troop_id, troop_id</enemy group 2>
Then you'd have a script call that does something like activate_group(1). This say you could do conditionals to set different groups of "random" enemies for different reasons.
would it still be any _Map Class along with what @Tsukihime stated?