We had a non rider for several rides a couple of weeks ago. I just went in and cancelled that person individually in the app. No problems.
Yes it is simple and easy to just cancel a LLMP for 1 member of your travel party.My sister doesn’t ride coasters or thrill rides. I simply cancel hers when we use ours and then book another one.
It is slightly more complex when trying to do this for a larger subset of your travel party. Yes some guests have run into the situation where they cancelled the wrong guest or multiple guests when rushing through the MDE process while making their way through the LL Queue and trying to book the next attraction for the group.
Dave