Electromagnetic Switching Toolhead (no replies)

I'm trying to configure "electromagnetic switching toolhead" for my costum 3D Printer construction. My Printer is running on the SKR PRO v1.1 + TMC2209 + Marlin Firmware 2.0.7.2. I have 3 tools that can be changed by a quickrelease system, locked by an elektromagnet. The Magnet is switched by a relay which is controlled by a digital pin on the board.

Nearly everything is working fine, but the electromagnet is not switched on/off at toolchange (by G-Code T0, T1, T2). I couldn't find any hint in the internet (or configuration), where the Pin for switching the e-magnet is defined. Does anyone know where to define that pin?

Because I had no success with "electromagnetic switching toolhead", I also tried "switching toolhead" (theoretically by servo, but I switch the relay and control the magnet instead) as plan B. --> here I can define SERVO0_PIN and should get a signal out of the defined pin (in my case "PA1" is used). I can perfectly control the pin by "M42 PA1 S0/S255" but the command "T0" doesn't switch on/off the pin. I have no idea why it doesn't.

My more prefered solution would be elektromagnetic switching toolhead.

I hope someone can help me solving this issue. If I forgot any detail please just ask.