I’ve setup RetroPie w/ controller No. 1. Now I’ve got a new controller (number 2) which is my favorite one. But Libretto emulators (like lr-stella for the Atari 2600) keep on using old controller No. 1. I think that is because Retroarch considers controller No. 1 to be my default one. I cannot get into a configure menu for lr-stella. For Stella that can be accessed w/ Tab. Not so in lr-stella.
Found out how. Run:
and choose: “Setup / configuration –> Configure input devices for Retroarch –> Configure joystick”. Then disconnect all controllers and connect the default one again.
 Ooops! Correction. I doesn’t! As soon as you connect your second controller again that one becomes the default! Darn it.