I finally understood why I am unable to calibrate my ext1 and 2 steps per mm. Found this in an older config file:
#define NUM_EXTRUDER 3
/** Set to 1 if all extruder motors go to 1 nozzle that mixes your colors. In that case only
<font face="Arial, Verdana">steps per mm and heater manager settings in extruder 0 are used! */</font>
#define MIXING_EXTRUDER 1
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<font face="Arial, Verdana">I'd like to be able to calibrate them independently, as they all use home made hobbed bolts and they are not identical.</font>
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