RolandP Thanks so much for the follow-up, Roland! You are so helpful.
I had a chance to talk to the Pilatus support line, and they were very helpful in case anyone needs to reach them.
As Roland mentioned, the ticket needs to be switched. But they could do it over the phone and cancel the original. Then you would buy the new one online then. Or, you can switch them at the new location (e.g. in this case, go to Kriens in the morning and ask them to switch the tickets. It didn’t seem the original seat reservation was refundable, so that’s the only thing that needed to be re-paid for (which was expected.)