Connecting an external switch to my circuit
KiCad is not a system design program. Which means it does not care what you connect externally to the pcb but only which things are soldered to the pcb to do so. There are a lot of options how to connect external stuff in general https://forum.kicad.info/t/how-to-connect-a-wire-to-the-pcb/18262



You can however still use KiCad to also document what is externally. Either by use of general graphics, by use of text comments or by placing symbols and wires but excluding the symbols from being part of the netlist via adding "#" in front of the reference designator.