Removing fuse 27, located in the fuse box in the top of the glove compartment behind that black plastic panel, turns off all the interior lights, including the ones in the cargo area. Seems odd that you have to remove a fuse to do this, though.

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2003 X5 4.4i
1992 Porsche 968
2007 328i
2014 Subaru Forester XT