The headlight switch on my 1984 BMW 633 CSi has a round knob, and the light switch on my 1986 BMW 528e doesn’t. The latter car has a bar that slides up and down. So, this is one aspect where the 5-series and 6-series cars don’t use the same part.
I asked my tech to replace the failing light switch on my 6-series car with a part from a 6-series donor car. When the work was complete, everything worked fine. But, when I saw the donor car, it still had its light switch. Puzzled, I asked my tech where he’d gotten the light switch from, and he pointed to a 1987 BMW 325.
After inspecting the one that he removed from my 6-series car to yet another one that he’d removed from a 3-series car, my conclusion is that these headlight switches are similar or identical.