Thank you for your question.
It is possible to show the Junior Travelcard/Children's Co-Travelcard in the SBB Mobile App instead of the physical card. To do this, the child needs its own SwissPass login. The Login can be created at swisspass.ch (the child needs its own e-mail address for this).
You can display the SwissPass card on up to three devices at the same time under SwissPass Mobile. It is not yet possible to display several SwissPasses on one application at the same time. However, to check them, you can first present your subscription via SBB Mobile and with your SwissPass login. Then log in with your child's SwissPass login and show your child's subscription.
Alternatively, we recommend that you install the SBB Preview app in addition to the SBB Mobile app and store one SwissPass in each app. This eliminates the need for logins/logouts.
We are aware that this solution is not optimal. We are currently working hard on a better solution for displaying the SwissPasses in one login.
I wish you a nice day.
Kind regards, GiorgiaB