Have been wondering that too. Some boards seem to have the P1 P2 and P3 in a line with the LED hole...so something to do with an LED display...and the LED inidcator mode and P3 mode settings in the controller software?
CR I believe is jumpered to ground to allow 'throttle hold' cruise control
Then there is:
SL is a Speed Limit override that is mentioned in the google doc and quote I put in above
DX3..well there is a pair of these and also the X3...still trying to find out about that and which one to use for the reverse function
XC, XC- Just found that...appears to be analogue speed output
I did read somewhere on one of the threads that Aux when connected to an LED powers up briefly when the controller starts up, and when under regen braking, so there was a thought given that it may drive a regen indicator of some sort
My 18 FET board is like this;