I don't know which switch/knob is which on a Vintage, but the extra ball knob sticking out of the e-brake boot is to adjust the heat into the cabin.
I use the word "heat" more as a suggestion, rather than reality.
Earlier Speedsters using a VW pan built before 1964-ish(?) had a knob just ahead of the shift lever for heat control, like this. This happens to be a real 1958 Speedster:
Here's a 356A dash, if anyone wants to fill in the switch functions. This is the same real '58 car but who can identify the knob just above the starter switch? It's never included on a replica.