Hello,
I realize this question was quite a while back but when searching for the same answer it pops up at the top of the search !
So Here is the answer for anyone else looking for it:
“This property can be used to set up Sight perception for teams. Currently, Affiliation can only be defined in C++. For Blueprints, you can use the Detect Neutrals option to detect all Actors, then use Tags to filter out Actor types.”