Will this be running in April 2020??
Looks like the last day of the winter season is 29 March, and they shut down until June.
https://www.mountains.ch/en/romantik-hotel-muottas-muragl/hotel/Opening-hours_timetable
SBB gives this message (in German) when you look at station info for Muottas Muragl for April 23.
There are no connections at this stop during the specified period. Please check your entries (date, time, direction, etc.)