Hello _Nik_
On the app, you must perform a log-out / log-in action to switch between accounts.
I suggest using two different apps: the SBB Mobile app and the SBB Preview app. The latter is used to test new features yet is fully functional. By doing so, you have both accounts set up at the same time.
I see many couples using both apps on their devices, to have their own and the partner’s SwissPass available on both phones, in case one phone is not functional due to the lack of sufficient battery. Cool, right?
Best regards,
Roland