Subtract or edit exercise minutes from Apple Fitness workout.

Sometimes Apple Fitness doesn’t ask whether to ‘end an exercise’ and I might forget. When it’s only a few minutes before I hit ‘end’ I ignore. But if I get called away and the exercise gives me an hour or so before I look at my watch and notice to end it ….is there a way to remove the extra time? Only thing I’ve found so far is a procedure using the iPhone but it’s dated 2018 and doesn’t seem to work anymore. Anyone know how to do this? And if so would it only work for that day or (if I get a response to this query a day from now…) would it still work ? Doesn’t happen a lot but I’m always disappointed that I can end a workout and actually SIT and do NOTHING for a hour or so and the Watch doesn’t prompt for an end to the workout! Thanks for any replies .