If you're missing Workout GPS routes or Health data after updating to iOS 14 and watchOS 7

Do you mean an itunes backup?.

I've the same problem with GPS running outdoor after installing watchOS 7 and then 7.0.1 too :(

frustrating

Make sure you do an encrypted backup in itunes as this also backs up your health and fitness data.

After you have re-paired your watch you can restore from this backup.