Every time my coach updates my plan or creates a new session, I test it for a few days, take notes in the Notes app, and then write her a document like this: https://docs.google.com/document/d/1rpgL3ciKw1LhHVZLqpCdYuocaM78nE_MP9X0uW-yD00/edit?usp=sharing to explain what I think we should change and why.
Writing all of that inside the app would take way too long. I really believe there are better ways for clients to share feedback — for example, a “make a suggestion” feature that lets you add comments to any exercise directly from the workout screen, change the order, or suggest substitutions/deletions.