On my stock printer (Sidewinder X1), when I pressed "cancel printing", it would pick up the tool head a little bit, park the nozzle, and move the bed to the back.

I replaced my mainboard, LCD, and new Marlin firmware. When I choose "stop printing" from the LCD, now it just stops moving. It doesn't park the nozzle and I'm not even sure if it cools down the heaters.

I'm trying to figure out where this is controlled....is it controlled in the LCD firmware, thus I need to hack the LCD firmware somehow, or is there a Gcode command for "stop printing", in which case, where is the macro that controls that located...is it baked into the firmware, or is there a text file somewhere?

So far I have not located any Gcode for "stop printing".

M524 kills a SD card based print job.

M25 pauses a SD card based print job.

I didn't find anything that will invoke a Marlin based macro when a SD card based print job is stopped/paused.

Marlin does allow creatng custom menus. You could use one of these to do the print job kill and then issue the cleanup commnds.