How to customize Bluez configuration for bluetooth remote

I have a Sony PS3 BD Bluetooth remote and it actually works great on Libreelec controlling Kodi out of the box (highly recommend it), but there are a few key mappings missing. In the Kodi forums it recommends modifying /etc/bluetooth/input.conf which obviously isn't possible on Libreelec since /etc is read only. I assume like most things in Libreelec I have to create a file in /storage/.config but I don't see any obvious candidates in that directory and I can't find any documentation. Does anyone know how I create custom bluetooth controller keymapings ?