We have a seat reservation from Montreaux to Interlaken, but we are going on to Lucerne. Do we need a seat reservation for the Interlaken to Lucerne portion of the trip? I think it is still considered part of the Golden Pass trip, but I haven't seen that people need a reservation.
You do not need a seat reservation for the Interlaken to Luzern train. You also do not need a reservation for the Montreux to Interlaken train either, but if you take one of the through GPX trains they are a good idea.
The Interlaken - Luzern train however is 10 cars long in summer, so enough seats for everyone.
Thanks Wengen all your responses to my crazy train questions. Leaving this morning from FL to NY to GVA.
You can get a seat reservation if you really want one. They cost 14 CHF, which is 9 CHF more than Swiss IC trains. I guess Zentralbahn figured they were leaving money on the table by not offering them to paranoid tourists.
https://shop.luzern.com/en/stories/luzern-interlaken-express