Damn, now I want to pick up a joystick I can use left handed to get the maximum experience out of this, my hotas is right hand only. As for the actionmaps.xml i already changed things up for something that works. The intended command was indeed to toggle free reticle. Works with left alt no problem. BTW I used the action mapper and didn't edit the xml file in an editor so I don't really see how it could be a syntax error. Also I tried binding that mouse button to weapon group 3, again no joy.
Action map included how it would have been