Many Garmin watches display heart rate recovery at the end of your exercise, but do not save this with the activity data in Garmin Connect. I have added this feature to 3 of my datafields. The MET datafield, Walking VO2max Test datafield and Aerobic (HR Zone) Timer datafield. The displayed value is the number of beats per minute by which your heart rate dropped 2 minutes after the end of your exercise.
MET datafield:
https://apps.garmin.com/en-US/apps/d487afae-e747-4cbc-ab3b-87f447a21234
Walking VO2Max Test:
https://apps.garmin.com/en-US/apps/3c135204-f323-4ea9-980f-c7b6660130d3
and Aerobic (HR Zone) timer:
https://apps.garmin.com/en-US/apps/042ab129-6ee3-4751-af14-527d74b20713