This one is totally reasonable. However, I have to decline this one, unfortunately. The reason is that I have added this to an app before for the exact reason you mention. But it became an absolute nightmare and I think ultimately killed the app. The problem was that this feature was abused and used in creative ways other than the reasonable case you present and what I had thought would be the case. What happened is that after saving a workout the app has a certain outlook on the future in relation to the past and present. Editing things after the fact starts to scramble the data, especially if the edits are more numerous. Quality control ultimately became an incredible challenge with this feature.