I have a similiar problem and found this thread. Thanks for the answer. Instead of opening another Thread for a similar problem i will just post here. However with your idea only 2 of 3 controllers work.
I followed your advice and used the joyconfig tool for 3 controllers (usb noname controller from bigben) In emulationstation it works just fine for scrolling.
The Controller configs i created with the joyconfig tool where stored at:
Unluckily in SNES games i can only use 2 of 3 controllers. It seems retropi wont like a 3-controller setup
Is there anything special i need to do, when i want to use three controllers?
I only want to play SNES with 3 controllers (got secret of mana und super bomberman ROMS, which are playable with 3 controllers on original SNES)
I Would really appreaciate some help :).