When finished click on Build this remap and download rehid.json
Copy rehid.json to a rehid folder on the root of your SD card
If you want 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
Create a rehid.json file with the remappings you want. possible options include:
"keys": which maps a key press to another key press. Possible Keys are: A, B, X, Y, SELECT, START, ZL, ZR, L, R, LEFT, RIGHT, UP, DOWN, CLEFT(CPAD), CRIGHT(CPAD), CUP(CPAD), CDOWN(C-PAD), CSLEFT(C-STICK), CSRIGHT(C-STICK), CSUP(C-STICK), CSDOWN(C-STICK)
For this example, it creates a box starting at x=10 y=20, with a height of 50 and a width of 100.
Other options include: "cpadtodpad":true maps the C-pad with D-pad key presses "dpadtocpad":true maps the D-pad with C-pad key presses "overidecpadpro":true makes it so games don't recognize the circle pad pro "homebutton": maps the HOME button to a key press
These Options can be strung together into a single line, for example:
Copy rehid.json to a rehid folder on the root of your SD card
If you want 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.