Two options: you can overwrite the previous camconst.json , or you can leave the previous one alone and put the new one into ~/.config/RawTherapee/

If you want to overwrite the previous camconst.json , you will find it in one of two places, depending on whether you compile RawTherapee yourself, or install it from a repo.

If you compile RT yourself, drop the new camconst.json into the build dir replacing the previous one.

If you install RT from a repo, which means RT gets installed system-wide, it looks like camconst.json goes into the “datadir” which is /usr/share/rawtherapee

https://github.com/Beep6581/RawTherapee/blob/master/rtengine/CMakeLists.txt#L45

https://github.com/Beep6581/RawTherapee/blob/master/CMakeLists.txt#L126