Hello IrisQ12
It is not possible to add the Swiss Travel Pass (note, not SwissPass) retrospecticvely to the SBB Mobile App.
Simply present your Swiss Travel Pass as a PDF document, or as a printed document to the ticket inspector, together with your physical passport or national ID card (no copies, no photos on smartphones).
Furthermore, your ticket ID has been masked. Never share ticket ID’s or photos of tickets on a publicly accessible forum such as this platform, simply to protect your privacy and to prevent abuse of the ticket itself.
Kind regards,
Roland