In the US, a “three-way” means two switches and one fixture. In the UK, a “three-way” means three switches and one fixture. So I’m a little bit confused since you’re linking to US switches but it sounds like you’re using UK terminology? In the US, one master switch and two add-ons would be a “four-way.”
Anyway, the following thread explains about networked auxiliary switches, which I think is what you’re asking