IIRC you could just drop your Key Commands in the preference folder root when moving from C4 to C5 and it showed up ready to rock next time you started Cubase? I was greated with a “file of the wrong type” moving from C5 to C6???
Don’t fear the cowbell, though! You can click the icon that looks like a folder in the Key Commands dialog, select to show all files and then select the KC file you saved in a safe place before installing C6.
Because you did, didn’t you?
Then it works