Hi fbelite1
The principle of the app is that you have the flexibility to check our timetable wherever you are. In this way, you can also be informed about the current situation of the desired connection ( for example, in the event of delays, cancellations, sudden platform changes, etc.).
So, you can plan your entire journey in advance, including the 60 minutes for the stopover, using the timetable on www.sbb.ch, or you can simply check the next better train connection to St. Gallen during your stopover in Zurich with the sbb app.
Have a great day. EllenvS.