My bed is 250mm x 227mm. I have gone through the header files in the Marlin and modified bed size no problem. I went and changed the auto level bed size thinking that is where the coordinates for the manual bed calibration would reside, it was not. I then poured through the GCODE and could not find any applicable commands to automatically set manual bed calibration. I therefore concluded that in must be on the Raspberry Pi, not in the Marlin code. I respectfully request that if I am correct, a screen to change the leveling points be added. I have zero problem leveling the bed now, but when everything else is completed this would be nice.