Sorry - I think I got it wrong. The import option is not needed.
When I installed Cubase Pro 8, I copied the Key Commands.xml files from an earlier version of Cubase. When I ran Cubase 8, my saved preset names were already available in the Presets drop-down list. I didn’t have to import them.
I think .key files were used in much earlier versions of Cubase. See the first few posts here:
Key Commands Files Issue - #2 by steve - Cubase - Steinberg Forums