HI all,
Good timing seeing this one near the top of the forum. We just added this feature yesterday in the latest beta release for our desktop apps! 
You will now be able to toggle the visibility of live heart rate data during a workout by using the “H” key on your keyboard as a shortcut. Heart rate data will still be visible in the completed workout.
Our beta apps can be downloaded here . Please note that this is desktop (Windows and Mac) only.