Seeing as I mostly used FSX/Acceleration, and not FSX-SE (until  my power supply died and took out my 4TB HDD), I know the setting was the same in both:
SHIFT+L for Panel lights (on/off). FSX-SE setting shown in attached image.

I will return to mostly using FSX/Acceleration once I get a new power supply that will give me the wattage I need to be able to use my BluRay-RW again, and I can then reinstall it.

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