Replacing scheduled workout ('unlink' command question)

I started another mtb marathon plan today. I have A Dog’s Life workout scheduled for tomorrow. I did it several times as part of my previous plans. I would like to swap it with another inspiration workout which I never did before.

In the past I did this by simply starting another workout and ignoring the planned one (removing it from the calendar actually). This time I would like to link that new workout to the plan. I wouldn’t think that it is possible, but I read a post by sir @JSampson If you unlink and then select another workout that is a similar time and add it to that date you can link and they will turn green Linked Activities in Calendar - Exclamation Mark Icon
I couldn’t make it work, however. I could unlink completed workout but I couldn’t link any workout back to the scheduled one (similar duration or not), even if I’d added the same one. Yes, the added workout turned green after completion (or orange if ended prematurely), but it is always like that for workouts added to calendar manually (no plan required).
Any chance to have it working (a new workout being connected to plan with that nice plan name on its tile in the calendar) or is that unlink command there just in case one would like to repeat (start over) the same scheduled workout (when something went wrong, like sensors failure, doorbell ring, etc.)?