Highlight part in activity zone where motion is detected (motion alert)

Because I am getting too many motion alerts with my doorbell, I am trying to optimize the size of the activity zone and the motion detection sensitivity level. But I do not know where in the activity zone the motion was detected.

It would be very handy to highlight in the video where the motion is detected. Then I can move the activity zone border (if the motion is at the border of the zone) and/or adjust the motion detection sensitivity level (if the motion is in the middle of the zone).