okay. you have triggers, and they have various ways of being 'fired', for example, 'west present' which means if a west-side loon wanders into the trigger area it will fire. fine.
triggers also have this thing called 'thislist', which is a list of all the loons in the trigger area who could fire it. so if you have a trigger, activated by 'west present', and a west-sided group wandered into its area, 'thislist' would hold a record of that group. all the loons in that group, or rather, all the loons in that group who are inside the trigger area.
i digress
if you make a trigger which is large enough to cover the whole map, say 5000 x 5000, and make it activate on 'east present', and in the 'on activation' field put
all_east = thislist
that means the variable 'all_east' now refers to all the east loons on the map.
so to change all their behaviours when another trigger is tripped, just put
{_x setbehaviour "whichever"} foreach all_east
in the 'on activation' field of that new trigger.
does that clarify?