As a direct answer: The KA 100 adaptor adds almost exactly 1 inch to the length of the KM 100 amplifier (body). The Lemo connector of the extension cable is about 2" long, and the cable itself comes out of that, so you'll need slightly more than 3" clearance beyond the tip of the body--see the attached photo.
But as John said this is the older version of Neumann's extension cable arrangement. Since it doesn't have a Lemo plug, it requires less space at the input to the microphone body. I wouldn't be surprised if the newer type of unitary extension cable also offered somewhat better protection from radio frequency interference.
--best regards