I was thinking maybe make a configuration plain-text file and store it in spiffs which will look about like this (just pulling this off the top of my head right now):
appearance.showWelcomeScreen=true;
appearance.showAnalogClockOnIgnitionOff=true;
appearance.dayAndNightMode=auto;
appearance.screenBrightness=230;
appearance.soundOn=true;
setMode.milesOrKm=miles;
setMode.clock=24h;
setMode.MGFcarType=MkI;
setMode.language=EN;
sensors.connected.windscreeenWash=true;
sensors.connected.lowCoolant=true;
sensors.connected.crankshaft=true;
I would then in my code fetch the configuration settings from the txt file in spiffs and use them to display my data on my screen. If I then decide to toggle different settings via my settings menu screen, the corresponding variables in the settings.txt file will be overwritten.
It's been a long time since I've done anything remotely to do with fread and fwrite (I used it a bit of it back in my days of coding web pages in php as a side job), but I'm sure there are neat ways of doing this in C.