Yes, you're right about findIf, it's not the quantity.
The trigger will activate only if all three mentioned units are absent from its radius. I am using this condition:
!(unit1 inArea thisTrigger) && !(unit2 inArea thisTrigger) && !(unit3 inArea thisTrigger)
But if I want to use a command like this one:
x_ inArea thisTrigger
to do the same thing. I had thought of that:
[unit1, unit2, unit3] all {!(_x inArea thisTrigger)}
Unfortunately, it doesn't work...