Not only have I wanted this for years I see similar requests going back for years.
The Garmin Connect App should track the last activity and the Recovery timer, showing it in realtime.
It seems so logical yet has never been added?
By the way there is also a bug in Garmin Connect App behavior in that the maximum heartrate shown for the day does not include activities.
ie. if the max heartrate in an activity is 170 but outside of activities the max heartrate was only 130, it will only show 130 and not 170
Why not split that long line and show both numbers, max outside activities and max in activity for that day?