Me and my team are currently working on a standalone watchOS App, where we are tracking workouts with HKLiveWorkoutBuilder. Just before calling the finishWorkout(completion:) method that saves the workout into the HKHealthStore we are saving some metadata when necessary to the workout.
However, we would also like to change the green value in the Fitness App that defaults to the workout duration to active/total KCAL just as it is visible on the entry saved from the Health App. The green value is displayed in the iOS' Fitness App list of the workouts just under the workout name as seen on the screenshot below. We have also done some research on the AppStore and there are 3rd party apps which saved workouts actually show the KCAL in the Fitness App, therefore it seems like there is some way around it.
Unfortunately we were unable to find matching HKMetadataKey in the docs, nor could we find any other possible solution.
We will be very grateful for any tips! Stay safe :)
Our team managed to get a response from Apple Engineers in this matter and they have said that there is no API to achieve that for 3rd party developers.