MKS TFT3.5 Custom button

[Asafbucak]

Hi, I have this issue that is I want to add custom button to open the lights and close them. I connected the led wires onto the main board. I found out the custom button option on config file. I suppose, I write gcode there. But I don't know what is the code and how to write in MKS TFT 3.5 config file. Could you help me with this situation please?

I am using;
Mks genL v2.1 motherboard
Mks tft3.5 touch screen