I don't think ribbon cables are used to connect the hinged part to the main body
If you look very carefully in the small gaps, between the hinged panel of the KN7000 and the chromium plated parts of the central fixed beam (near the Power Switch and SD Card receptacle), you will see a bunch of insulated wires. These are obviously the connections between the panel and the main body electronics.You can probably see them best, when the panel is closed. Using this method of connection means that the cables are not really subjected to any great amount of strain since the bunch of wires is just allowed to freely rotate on their axis, through about 120 degrees. Two of my laptops use a similar principle as did a Yamaha PSR6100 which I owned many years ago.
Although there are around 140 Buttons and other controls on the hinged panel, this does not mean that there will be connecting wires from every control, to the main electronics in the KN7000 body. The controls will most probably be multiplexed within the hinged panel and fed as a data stream, down a limited number of wires, to the electronics in the main body of the instrument.
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Willum