I didn't make the train I was aiming for, which meant that not only the supersaver ticket but also the bike reservation was no longer valid. And at least one booked bike parking space rode south untouched. But that's not the point here.

The most recent train journey by bike brought a new insight: this winding route through the SBB website: Home page > Travelcards and tickets > Seat reservations > Self-loading bikes > Buy bike seat reservation Switzerland > Integrated into the explanatory text there is a link to the bike seat reservation for intercity connections in Switzerland and for the Swiss section of international trains. A closer look reveals that it is the same address that rides to the same web form. The fact that the two separate links are identical and refer to the same web form fits in with the complicated booking process.

Recommendation: App for Swiss IC, website for international trains

So if you prefer to book the various tickets and reservations on the computer rather than on the phone, you will find an extra form here to make the infamous bike space reservation. Why it is not possible to buy bike tickets and reservations together with the route ticket on the same interface remains SBB's secret. At least this is now possible on the app - but only for Swiss IC trains. It is still not possible to reserve a bike space on an international train via the app. The link above provides valuable assistance here.