Windows 7 finds the Sub37 out of the box with its own drivers. But since I want to use the Sub37 Editor inside Cubase, I need to install the Sub37 USB drivers (Moog_Sub_37_USB_DriverSetup_v2.23.0.exe).
However the installer does not find the Sub 37 even though Windows has already found it (it’s available as USB/MIDI Devices and it shows under System/Device Manager).
Ofcourse I tried uninstalling the default Windows drivers etc.
What can I do here?
Solved it!
The new Firmware released just a couple of days ago, version 1.2, fixed it! I had to update the Sub37 via another computer though, but then it worked fine in my DAW including the Sub37 Editor in Cubase. 
And also, I am using Sub37 USB MIDI Drivers v3.30, not 2.23.
I’m glad your problem is fixed, but what makes you think that firmware 1.2 was released only a couple of days ago? As far as I know Sub 37 firmware 1.2.0 was released in April of 2016.
The website said release date was 2016-01-30 when I checked. Now it says 2017-02-13. Something fishy is going on.
For a very long time after the release of firmware 1.2.0 and the software editor these versions weren’t mentioned at all on the website. They only added these entries recently, but they were originally released in April 2016.