The easy-switch feature needs some kind of controls in the software.

The logi+ software shows that the number one slot is taken by my Mac Mini, which I don't even have anymore. And then I read from the internet that the bluetooth should be toggled on and off from the Mac for it to disappear from the - I assume - memory of the keyboard.

I have the same problem in my MX Master 3 mouse, first slot is taken by my Mac Mini which I don't even have anymore.