1) What does the electrical cable assembly shown in your first three photos at the top have to do with a lumbar support? Don't take this question the wrong way, I am sure it has something to do with the lumbar support, otherwise you would not have included the pictures, but I am too stupid to figure out what it does.
The VAS 5094 is to keep an accidental static electrical charge from deploying your side airbags. You are hardly stupid!!
2) If I order the 'repair kit - P/N 1J0 898 943A that you mentioned in your post of April 06, 2002 at 21:02, does that provide me with everything I need to retrofit a lumbar support?
I'm not sure right now
There is a large support wire that goes at the bottom of the seat frame that one needs. It supports the bottom of the two main vertical support rails. I got these parts at a junk yard. I will know Tuesday or Wednesday what comes with the Kit. If you get one, please post pics so I can see the parts!
3) What about installation and final trim work of the control for the lumbar support? I am assuming - perhaps incorrectly - that the lumbar support is controlled by a knob that protrudes out the outboard side of the seat back, somewhere above the recline knob and below the side airbag. Does the repair kit include the knob, trim bezals (if needed), etc.?
Yes, the knob is just above the seat recline and below the airbag. The knob needs to be ordered seperately, it's $5 USD. That's all you need for final trim work. I did some reinfocing of the seat fabric from the INSIDE with sewing iron-on adhesive and some "cross-stitch" canvas/fabric.