If you remove the diode and replace with jumper (or better would be 1-to-5k resistor ) , you can do without the external pull-down resistor and wire the switches between the arduino pin and Gnd.
If you remove the diode and replace with jumper (or better would be 1-to-5k resistor ) , you can do without the external pull-down resistor and wire the switches between the arduino pin and Gnd.