Got these 2V push-buttons for bypass & turbo. And a meter with 5-7V LED.
So I have 9-11 volts in total and I wanna connect it to the 12V I have available on the ctrl-board-LED output.
How can I add them in parallel without dimming the meter-LED whenever buttons are pushed down?
You don't have the LED's inside the DPDT switches connected in series, so LED forward voltages don't add up to your '9-11 volts'.
Allowing maybe 10mA per LED inside the switches for a parallel connection, each LED needs a current limiting resistor of (12VDC supply - 2VDC LED forward voltage)/0.01A= 1000 ohms.
Inside the meter are two series connected LEDs with -depending on LED-colour- 5-7VDC forward voltage. Assuming maybe similar brightness and again allowing 10mA, the current limiting resistor for your meter illumination will be (12VDC supply - maybe 5.7VDC LED forward voltage)/0.01A= 630 ohms. Lesser allowed mA=lesser brightness, exceeding the max allowed 20mA parts limit will let the smoke out.
You DON'T connect these to the 12VDC spot on control pcb. The 78L12 vreg isn't build for this additional load.
You connect to the optional 12VDC aux supply spot on main pcb (and without the 7812 voltage regulator installed, there is no aux 12VDC).
The LEDs inside the switches only use the switch housing as a carrier. If these are illuminating or not has nothing to do with the switches status (they could be rhythmical blinking or show an overload condition or whatever else), except you hook these up accordingly. For your bypass switch you'd need 2 switch poles for the gssl-circuit and a 3rd pole for powering the LED. The switch only has 2 poles, so you'd probably use an additional DPDT relay for the else missing pole. The supersidechain filterboard already has a provision for this relay and protection diode on board, else a piece of perfboard, apropriate relay and diode will do as well.
Good luck
(must have been answerd a LOT more than 10 times...)