Whats the system called that does async processing?

Development Programming & Scripting C++
2 

FNotificationInfo Info(*FText goes here*);

TWeakPtr<SNotificationItem> Notification = FSlateNotificationManager::Get().AddNotification(Info);
if (Notification.IsValid())
{
	Notification.Pin()->SetCompletionState(*SNotificationItem::ECompleteState goes here*);
}

I don’t believe the call itself is done async - blocking the main thread will of course block the refresh/display of these messages.