To trick TFT into thinking it has a nav, you need to implement a LIN slave that responds to IDs 2Dh and 28h (hexadecimal 2D and 28). Below I am giving the correct response. I have done it, to control my navigator app through the wonder wheel. However, the software of the bike must be "ready" for the nav. This is standard for bike that comes with the cradle, like a GS, but not for a sporty bike like the S1000R. Mine was not ready, and I had to ask the dealer to make a software update and check the corresponding feature. Once the bike is ready, and the LIN bus that feeds the Nav gets the correct responses, the TFT will show a blue TFT icon on the top left. When you make a long up press of the Menu button, the TFT icon changes to NAV. At this point the LIN bus carries the signals of the wonder wheel, coded into the frame with ID 14h.
Here the needed responses;
Slave response to Master ID 2Dh: 01h 15h 15h 00h 00h 00h 00h 00h (8 bytes)
Slave response to Master ID 28h: FFh FFh FFh FFh FFh FFh 00h 00h (8 bytes)
My implementation uses an Arduino Nano ESP32 to implement the LIN slave, interpret the wonder wheel movements, and translate them into bluetooth commands (arrows up/down/left/right and enter) to control Scenic (the navigation app that I use and that works great for me).
I intend to publish everything (the electrical circuit, the Arduino code, and the code for a 3D printer). I don't know yet in which forum and in which format I should make all this available. Suggestions are welcome.