TrainingPeaks used to have the concept of "Breakthrough workouts". I'm looking for a similar concept, but the ability to show this clearly in the training calendar.

Ideally the calendar would have layers that users / coaches to toggle on and off, but this could also be done by manually tagging individual workouts. For me 3 layers would be perfect:

1) Priority - the minimum workouts that must be done
2) Recommended - if the athlete has more time, what they should do next
3) Optional - only consider doing once everything else is complete

Then have on the calendar ways to show these different categories / layers (e.g. Priority workouts are shown as normal,. Recommended workouts are a faded / greyed appearance, and Optional workouts are different again.