The tool is open source and available on GitHub.
What it does
I use an 8BitDo Zero 2 as a remote for reviewing Anki cards, watching lectures and presenting slides. Pad Map shows the controller and the key each button sends, and lets you choose what each button should do. You can pick an action from a library or record any keyboard shortcut. Modes give every button several jobs, and one button can cycle between them. The page then generates a Karabiner-Elements rule to paste in, which also shows the current mode on screen whenever it changes.