A patent discovered by Nintendo Patent Watch showcases a handle with a rotating disc for Joy-Con 2. Attachment is ensured by two magnets and tracked by a mouse sensor through a window. The clickable wheel is also tracked using a sensor via a gear mechanism. The click is transmitted via the SL button, and a separate button is provided for S2.
It is important to note that patents are just patents. Nintendo registers them constantly, and many never turn into real products. Sometimes such patents leak into the network, as in this case. The documents were filed in early 2024 but published recently. Nintendo has not yet commented on the patents themselves or the rumors they have caused. In the past, the company has never commented on patents, and this is unlikely to change.
The purpose of the technology is still unknown. Perhaps it is intended for fishing games, but it is unlikely that so much effort would be spent for this. Some speculate that this could be a revival of Kuru Kuru Kururin or other retro projects, but there is no exact explanation yet.
It is highly likely that the concept will remain at the idea stage. But with Nintendo, you can never be sure: the company sometimes releases unusual equipment, like Nintendo Labo.