Whats TriggerUnit's variable name?

You know how GetLastCreatedUnit() refers to bj_lastCreatedUnit any idea what GetTriggerUnit() would be referring to?

GetTriggerUnit() is not a variable, it is a native event response, that means that 2 triggers can have different values of triggering unit at the same time

so GetTriggerUnit is multistanceable? and the only way to set a trigger unit is to have a unit set off the trigger?

Yes, that's true.