Ok, so here are my findings (XPlane 11): There is no auto pitch leveler function.
The wing leveler modes from the XPlane 11 menu, are not real "roll to neutral". When enabled, they just keep the roll to whatever it was at the moment the button was pushed. So if you are in a turn, it keeps the roll where it is. The real wing leveler is activated via the command: "sim/autopilot/override_center" which has no keyboard or joystck bind available directly from the XPlane menu. I ve been able to map the latter command to the GFC blue LVL button by editing the RealSimGear mapping.ini file and associate the correct roll state (#2) by redefining the dataref next to <0 line in the mapping file, that drives the LED light above the LVL switch on the actual GFC500). So it works 50% as expected rather than 0% before I changed it.