Workout prescription using custom zones is live now. The “Add Step” dialog has been upgraded to show custom zones and zone names.
This only works for zones using the Power, Heartrate and Speed streams.
If you have several sets of zones active for a sport and they have overlapping zone ID’s then the zone from the first zone found is used, in the same order as on the /settings page.
There is a new checkbox in the dialog to use the pace units for the sport instead:
You still need to enter zone values in meters/second if not using a factor of an anchor.