I don't have a schematic as it is very simple circuit wise but definitely not an easy modification for beginners to try!
WARNING: the following instructions are NOT for beginners or someone who is inexperienced in doing panel/circuit modifications and PCB rework. Attempting this will definitely void your warranty! If done incorrectly you could cause your 569 to operate poorly or become totally inoperative and useless. I am presenting these instructions based on my own experience but I take no responsibility for their completeness or correctness and if you attempt this you agree to make no attempt to hold me responsible if it doesn't work out. Also, Moon Modular, their dealers and distributors will also not be held responsible for end user damages caused by modification attempts. Note that this modification has only been briefly tested for less than a day and only by myself on an older revision of the PCBs so unexpected problems with using this modification may arise in the future.
I'll just give the basics, if you aren't sure what to do from the following description you probably shouldn't be attempting this!
1) At a minimum remove the main PCB and clock PCB (removing ALL parts from the front panel is recommended)
2) Add a switch to the front panel for row 4 and optionally add a switch for row 3 also.
3) On the main PCB, lift the end of R27 that connects to IC9. This is row 4's transpose input and optionally do the same for R36 which is row 3's transpose input.
4) Connect wires to the ends of resistors and also to the solder pads the resistors were previously attached to and connect to the new SPDT switches. Connect the resistor's wire to the switch's pole and the solder pad's wire to one of the switch's throws.
5) Connect a wire from a ground point to the other throw of the switches.