I still do not know of a way to do this in TR, I don’t think it is supported. Looking at SYSTM’s website does not confirm whether their system can do this either (implies that it can’t as it talks about RPE in it’s run workout section; nothing about uploading to Garmin which I would have thought would use HR rather than RPE).
I am not aware of a platform that does this currently - let me know if you know of any.