My previous post was about adding an extra switch on the indicator panel. Another option will be adding a switch to the cluster switch panel, located on the left side of the dash.
I checked the construction of the cluster switch and here are a few thoughts.
There is an empty space on the left side of the enclosure. It is big enough (27mm x 30mm x 27mm) to fit a standard rocker switch, something like this:
You just need to make a cutout on the faceplate and drill one hole on the side for the wires
PCB on this switch has provision for all 6 buttons.
Unfortunately, the unused button covers are designed in such a way, that it will not be possible to use them. Of course, it is always possible to recreate and 3D print moving buttons, but it will be hard to get the same nice surface finish. It will also be possible to get an extra switch and relocate the moving plastic parts, but they will have the same icons, so it will be confusing.
The connector on PCB has two unused holes for additional pins, which will be handy to get wires out through the connector.
The “relocating method” will also require the use of an extra microcontroller, because the buttons connected through resisters network to the single pin. However, this implementation will be relatively easy.
Another idea I can work on is converting unused buttons into touch sensors; similar as we can find on modern TV sets. This is a relatively simple task and appearance will be intact.