I found a few other threads on this in device forums, but the feature request for this forum would be:
When all-day heart rate is available in your Garmin Connect account because you have a device that tracks it, but there are gaps with no data from the device, then GC should try to fill those gaps with heart rate from an activity recorded with another device. E.g. I take my Fenix5 off to go on a bike ride but record the bike ride on my Edge 520, GC should use the heart rate data from the Edge to fill in the all-day heart rate data. There should only be gaps if there is literally no heart rate data available.
