@clocey, There is no python. It is all Arduino “preprocessed” C/C++. The Marlin file structure is kind of a mess and the Arduino environment really sucks for trying to make sense of it. It took me a lot of poking around and searching with Ultraedit to start to make sense of it.
My only modification was to fix the status so it would display “Mostly Printed CNC OK” at the bottom. I’m just ignoring the printer temp and fan icons on my Full Graphic LCD.