Hi @Robert update on “all required electronics and leds are present” I’ve pulled apart a 3 switch module with 2 factory switches present and 1 blank and there aren’t the leds or components for the blank switchYou just need to get 2 inserts for your spare(currently not used) buttons.
On MQB(like your T6.1) all required electronics including micro switches and illumination and indication LEDs are present for all switches within one module (set/raw of switches).
Have a look below at the video done by Mateusz on his Golf MK7 (also MQB).
Exactly same principle applies to all T6.1.
And all inserts are the same for all T6.1 dash buttons.
If you have Start/Stop disable module installed, you can recuperate one insert as you don't need to press S/S button anymore.
Edit:
The available output pin for each button microswitch produces GND when depressed. This can be used for activating any FLIP-FLOP relay module (aka latching relay).
See below
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Hope this helps