All the Cheats are provided by GameHacking.org.
Change this dict from the .github/download_cheats.py script on the develop branch:
It needs to map the file name from https://gamehacking.org/mister (left side) to the core folder name from MiSTer (right side).
https://gamehacking.org/mister
The result of that change will show on the main branch. You may always check the logs on the Actions tab