I Know that full info feom powermeter device (such as right/left balance,etc…) may not be usable during a ride (maybe yes by many, but you could displayed into your garmin device)…
But it will be great to be introduced in the fit file, in orden not to lose this info.
Workaround - dual recording (my solution - p2m NGeco, BLE recording Zwift, ANT+ recording Jepster App for Android, with L/R balance).
Depends on your hardware, of course.