GENKI CONFIRMS MOUSE FUNCTIONALITY
https://www.theverge.com/2025/1/8/24339396/nintendo-switch-2-genki-ces-2025
Tsai also tells The Verge that housed within the mounting channel of the Joy-Cons is an optical sensor, and by using another attachment the new Joy-Cons may offer mouse-like functionality. It sounds a bit like what Lenovo does with its Legion Go handheld.