The scene: You've just scored an awesome goal - or the tracking headshot you just was off the charts and you don't want to forget it.
When that happens and you play for a long time after the clip sometimes gets lost.
Solution: A hotkey that can be pressed that tags the clip, can be pressed as it happens or within a few seconds after it happens.
This could also provide a quick set of clips for a streamer to highlight and post or for some friends who want to get their best clips of the session up on their prefered social media.