Updating Marlin Eeprom settings:
It sounds like a noob question. Let’s assume I cannot access the printer controller by USB. Is there a way of loading M commands via SD card?
Sure, it’s just like any other gcode. Just write your . gcode file and upload it to the sd card. It’ll be a bit more difficult if you need to check settings first, but you could write a file that only has M503 in it.
@Stephanie_A Thank you for your reply. That sounds good 
Two more questions:
#1 Will M503 write the settings to the sd card?
#2 You mentioned that it’ll be more difficult if I need to check the settings first. That sounds like this would be possibile. 
Actually I would like to load a file, which reads the settings (M212 Z value), then add an increment of 0.1mm and finally store it with M500.
M503 displays eprom settings. Their documentation has improved drastically. See http://marlinfw.org/meta/gcode/
http://marlinfw.org/meta/gcode/
I don’t think you can do math in gcode. You might need to write a separate file for each height.
@Stephanie_A OK, that’s fine for me. I can place a bunch of these files on the sd card.