Magic Mouse 2: how to enable middle click? (Magic Prefs doesn't anymore)

Looks like they have ruined another nice product.

You need to install additional third party application. I found this (free) little app GitHub - cl3m/MiddleClick: Emulate a middleclick with triple tap on MacBook trackpad and Magic Mouse.

It works with a 3 finger touch and not a middle click.

I just was able to do it with Better Touch Tool: http://www.boastr.net/

I am surprised that the Magic Mouse 2 is even working on your Mac as it needs OS X El Capitán as its minimum OS X version.

Is your iMac running El Capitán?

ALL of the new Apple 2nd gen. wireless input devices NEED OS X El Capitán as the minimum OS X requirement.