need help with code for controlling a hydraulic press mode

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3 
  if (digitalRead(P1) == LOW) HP1 = 1;
  else HP1 = 0;

In other words,

   HP1 = !digitalRead(P1);

  boolean button_P1 = handle_P1();
  boolean button_P2 = handle_P2();
  boolean button_P3 = handle_P3();

Pass an argument to ONE function - the pin number. Don't write three nearly identical functions.

  boolean button_S1 = handle_S1();
  boolean button_S2 = handle_S2();
  boolean button_S3 = handle_S3();

Oops, make that 6.

  buttonState = digitalRead(buttonPin);

Switches work so much better than buttons. The names do not contribute to understanding what the code does. Sure, you are reading a pin, but there is no clue as to why. What is connected to that pin? FOR WHAT PURPOSE?