Is there a way to copy all my key commands from N11 to N12, or do I have to enter them all in again?
Just copy them.
Thanks for the reply.
Where from?
From the Preset-folder:
You can also create a profile in N11 and then export it to N12. Most but not all of your settings will be copied over but recently I’ve found that feature to be buggy with N12.
I’ve never used this ‘profile’ facility before and using it I managed to completely mess up a lot of preference settings and who knows what else.
Perhaps I could ask a different question:
What is the name of the file that stores my Nuendo Key Commands and exactly where should it be on my Windows-10 PC? I would simply like to copy the file from N11 to N12.
Did you read the specifications in the link I posted above? As soon as you have saved your NU11 Key Commands under a specific name, you will find this file in the Preset-folder with the name “Key Commands”. 
You’re on Windows so go to the Program Menu and look under Steinberg and Nuendo. There is a link to your setting folder there. Open up the N11 folder and the N12 folder, click on Presets, then Key Commands and copy your keys from the Key Commands folder. HTH.
Ditto what Wheels said.
Or:
Copy
C:\Users*UserName*\AppData\Roaming\Steinberg\Nuendo 11_64\Key Commands.xml
to
C:\Users*UserName*\AppData\Roaming\Steinberg\Nuendo 12_64\Key Commands.xml
Ah Ha! Thanks.
I’ve been trying to copying from C:\Program Files\Steinberg\Nuendo 11 to C:\Program Files\Steinberg\Nuendo 12.
I’ve always failed to understand why this sort of housekeeping is not done automatically as part of each major version update. Each update should seamlessly carry all basic setup data from one update to the next consecutive one - it would make for a much smoother and less confusing update process.