Hi@“x”#p15846
You can travel with a saver day pass on the GoldenPass Panoramic Train from Montreux to Montbovon. No it is not mandatory to have a seat reservation. You can board the train with this ticket an sit on every seat, which is not reserved by another person.
On days with lots of people travelling (f.e. during the school holidays or on weekends with nice weather), it can be recommendable to make a seat reservation.
Have a nice trip.