Application "loss of focus" called something else?

I mean, it must be, because I can’t find any information about this when I search (maybe my Google-Fu is weak, though).

Here’s an old question with no satisfactory answer:…6482/view.html

And here’s another more relevant question, with also no satisfactory answer (not going to custom code C++ for this, and also, hello Windows Gaming Overlay?):…4148/view.html

The only thing I found so far is this, and it doesn’t do anything for me in Windows:

So, maybe I just don’t know the correct name for it in Unreal? What is it called when you alt-tab away from the game? How do you get events for this?