Cura now supports Relative extrusion via a checkbox in the settings menu. Might be under experiential (They moved it once).
It works perfectly fine, even without M83 in the startup Gcode. Need M83 in config.g though. Of course.
Must invert the signal “i1” when using the pins and not the Duex to connect the BLTouch.
The test signal is S120 and not S60