This only way to do this is by creating the workout ‘by hand’ in intervals.icu (or another platform that allows you to export a .zwo/.mrc file etc and then import it to intervals.icu) or by means which will be against the terms of service for TR and copyright etc.
I think the use of “curve” from the OP is confusing here. I think the OP is wanting to see actual vs. planned completion of a workout - something like this…
To do this I had to create the planned workout in intervals.icu