I can’t find any Preference, Setting, or Command that lets me add/remove/edit key bindings.
The process for this is the same as for Sublime Text but there are not currently any menu items for commands that would open the appropriate files. Possibly this could be because in Text those are accomplished via plugins and Merge currently doesn’t have plugin support.
If you use
Preferences > Browse Packages you can find your
User package and create appropriate files there. The official documentation has more details and examples for how this works.