Hello CJD
This is not possible after purchase. It only appears if the ticket was purchased as a registered user.
You should have received a purchase confirmation e-mail. There might be a link to add the pass to the wallet.
However, working as a ticket inspector, I can tell you that the most convenient way to check tickets is by a digital PDF saved on your phone. It is often difficult to scan the wallet QR code.
Please kindly note, your Swiss Travel Pass needs your physical passport (no copies / no photos of it on smartphones) upon ticket check.
Kind regards,
Roland