Karl said:
That long rear slot in the toolbox is for an alignment tool (sorry I don't have any details) that's not given to US cars.
Are you talking about the wheel alignment tool? This is a metal rod with a plastic cap on the end. It's used in mounting the wheels. The plastic cap fits into one of your lug bolt holes, with the metal rod sticking out. The wheel can then be hung on the metal rod while you put in the other four lug bolts. I've got one; I think they came with M E36s, but I don't know if they come on M E46s, now that they've ditched the spare.
On my E36, I also have a long, U-shaped piece of stamped metal in the toolkit (long and flat with the sides curved up). According to TFM, this is used to manually extend the rollover protection bars in convertibles. I assume that the E46 cabrios have something similar, but I don't know.
My car (which was originally Euro delivery) also has a warning triangle. The triangle is pretty large, and comes folded into a blue plastic case approximately 2" X 4" X 18." On the E36 cabrios, it sits horizontally/longitudinally in a slot on the left side of the trunk.