This is a vestigial function from antique times, when pterodactyls still roamed the land. I think it was for importing Cubase VST key command files into Cubase SX.
Now, you should be able to save a key commands preset in C9.5, and copy it manually to the C10 key command presets folder.
e.g., from
%Appata%\Steinberg\Cubase 9.5_64\Presets\KeyCommands
to
%Appata%\Steinberg\Cubase 10_64\Presets\KeyCommands