I think this is an interesting question. Can a tourist holding a Swiss Half Fare Card, select the option ‘Half-Fare Travelcard ½/3-year’ for the Reduction drop down to get the half fare benefit? To me it is still not clear, so would appreciate your feedback.
Per the instructions on this website https://www.sbb.ch/en/help-and-contact/produkte-services/offers-for-tourists.html, you can create a sbb.ch (SwissPass-login) account, purchase a Swiss Half Fare Card online while signed onto your sbb.ch account (SwissPass-login), and manually update your account with the ‘Half-Fare Travelcard’ as your Discount Card. Then it appears you get the same half fare benefits as a Swiss citizen holding a real ‘Half-Fare Travelcard’.
When booking travel from Spiez to Milano Centrale you are directed to the SBB Ticket Shop site, and have the option to sign on with your SwissPass-login or the Ticket Shop login. If you sign on with your SwissPass-login, it appears that the Ticket Shop site only uses your name and email from your sbb.sh account, not that you ‘have’ a Half Fare-Fare Travel card. You are presented with the Reduction option to select your discount card as shown in @rushikeshagashe post. It seems like you should be able to select the ‘Half-Fare Travelcard (½/3)’, since you were directed how to manually add it to your sbb.ch account (SwissPass-login) per the website instructions noted above.
If you select the ‘Half-Fare Travelcard (½/3)’ option, you are presented with an offer where the pricing seems to take into account the half fare price benefit for the Spiez to Domodossala part of the ticket. The discount is not applied to the Domodossola to Milano part of the ticket. (Note: this is where the Spiez to Milano route option has 0 changes). It seems like you should get the same benefit if you have a Swiss Half Fare Card. Or is there something special that this half price benefit only holds when you actually have a real Half-Fare Travelcard and you book a ticket that has an international part, ie, the conductor actually differentiates between the Swiss Half Fare Card and the Half-Fare Travelcard on an international route?
Thanks for your time on this. It is appreciated.