Have you had a look at this type already: https://multimedia.3m.com/mws/media/22045O/3mtm-round-shielded-jktd-disc-wire-cable-3750-series-ts0072.pdf?&fn=ts0072.pdf
With 5 bits you can decode 32 keys, see attached mapping table for the cx85. Adding the trigger input might give 6 bits and 64 key values.
on the driver side you can map any combination to any key value.
I sent it to @Farb and he is in the process of scanning it.
Actually he already made a disc image of the floppy which is equal to the image he already has therefore confirming it and the manual will take some more time.