I'm a complete noob as regards Linux, but I've got a Pi 3B that's currently only set up to run Kodi under LibreElec. It's actually got three 2.4GHz IR remotes (and a Bluetooth keyboard) connected, and they all seem to work together perfectly happily.
It turns out that unless I need to type actual text (search strings, for example) I can do just about everything I want using this really cheap one, which I find far more ergonomic than the others...
BUT it seems the "hamburger" button (the one with three lines, above the "house/home" button in the pic) isn't recognised at all in Kodi. And I've come to realise that if I could only remap that key so it was interpreted as keyboard character C (to invoke context menus), that would vastly improve my user experience.
I have a Win10 desktop PC that I can install the IR remote on if I need to use a utility to find out what scan-code(s) are generated by that hamburger button. I can also use the PC to explore / amend files on the 16Gb card the Pi boots from, but I don't know how to do this using the Pi itself.
Is there any way I can remap that button to do what I want?