With this any time you press X+Y, R key would be triggered, and any time you press the SELECT button, both L and R would be triggered.
Possible Keys are: A, B, X, Y, SELECT, START, ZL, ZR, L, R, LEFT, RIGHT, UP, DOWN, CRIGHT(CPAD), CLEFT(CPAD), CUP(CPAD), CDOWN(CPAD)
Copy rehid.json to a rehid folder on the root of your SD card
If you want to the remapping to be used for a specific title, copy rehid.json to rihid/(title ID)/ instead. You can find the title ID of your game using 3dsdb
Troubleshooting
An exception occurred
If your console crashes while booting with "an exception occurred" and the "current proccess:" is hid, you may have an old version of rehid thats causing issues. Look for and delete /luma/titles/0004013000001D02 and /luma/titles/0004013000003302. If these don't exist, you may have a more serious hardware issue, join the Nintendo Homebrew Discord and ask, in English, for help.