Jadawon or Idris, I have an DIY x-arcade and ran into the same problem as you with not being able to use the bracket keys[ ] in the retroarch.cfg. I reprogrammed the x-arcade, but the problem is that if the unit is shut off and then turned back on, you have to press the load button twice to load the configuration.

I’d really like to be able to power the system up and play games without having to load a x-arcade configuration every time. I was wondering if you guys managed to find a better solution.