This is exactly why I don’t use end stops and touch plates. Just kind of a hassle, it is much easier to just use pause commands in your gcode for tool changes, and if you aren’t doing tool changes there is not much need for a touch plate.
To test three axis on a ramps board, you will need a minimum of 4 wires. Ground, x min signal, y min signal, z min signal. If you use estlcam firmware I think he just uses one set of pins for all axis.