I have a 2017 T6 Euro 6, I went through the process of changing the Byte 15 to D3 from E6 as detailed above.
As soon as I clicked 'Do It!' I got 3 lights lit on the dash, ABS warning, ESC Off and another ESC warning symbol, which was a worry as I don't have an ESC On/Off button!
The TPMS active box was ticked in Instruments module already.
The Tyre Pressure option appeared in the MFD list but repeated attempts to set the tyre pressures resulted in a 'Failed to store settings' warning.
So I unticked the box in Instruments, saved it, and turned off the van then restarted it, tried to store the pressures again and it failed again, so I went back in and ticked the box again, saved it and switched off again.
This time, on restarting the van, I could set the tyre pressures. (whew!) so all is good!
One thing I noticed looking through the various options was a Normal/Robust/SuperRobust & Sensitive options under the Adaptations list for TPMS, Anybody know what they are?
I also turned off the Seat Belt warning as well (it seems there are 4 version options for that one in Instruments adaptation, no idea what the differences are but mine was set as version 4) but now disabled/not ticked (under instruments/coding/byte 1)