The N-Scale Nerd says:

If you’re using the Arduino, Stepper-motor module, I tweaked the code to include a FWD and REV button to manually swing the table. You’ll have the stepper.h file in the Arduino library.
For your application you’ll have to include an input for your Hall Effect sensor, too.
The other issue is to find the right shaft-coupler for the turntable. The diameter of the Arduino stepper motor is 5mm.
Here’s the code…

//FORWARD/REVERSE Control of Stepper Motor – Rev XX
//26/3/2020 – Use Rubber coupler to motor. (StepsperRev set to 10)
//24/4/2020 – Use Lego gears to motor. (StepsperRev set to 64)
//27/04/2020 – Found a plastic shaft-coupler – Works a treat!
//26/05/2020 – Change StepsPerRev to 5

#include

// Constants used to set pin numbers:
const int CWbuttonPin = 2; // the number of the Clock-wise pushbutton pin
const int ACWbuttonPin = 3; // the number of the Anti-Clock-wise pushbutton pin

const int stepsPerRevolution = 5; // 10 – Gives ~10 degrees;64;200;change this to fit the number of steps per revolution
// for your motor

// initialize the stepper library on pins 8 through 11:
Stepper myStepper(stepsPerRevolution, 8, 10, 9, 11); //NOT 8, 9, 10, 11 as shown in examples!!!

// variables will change:
int CWbuttonState = 0; // variable for reading the pushbutton status
int ACWbuttonState = 0; // variable for reading the pushbutton status

void setup() {
// put your setup code here, to run once:
pinMode(CWbuttonPin, INPUT);
pinMode(ACWbuttonPin, INPUT);

// set the speed at 200 rpm:
myStepper.setSpeed(200); //60 initially
}

void loop() {
// Here’s the main code, to run repeatedly:

//Clockwise Push-button code
// read the state of the CWpushbutton value:
CWbuttonState = digitalRead(CWbuttonPin);

// check if the pushbutton is pressed. If it is, the buttonState is HIGH:
if (CWbuttonState == HIGH) {

myStepper.step(stepsPerRevolution);//Rotate clockwise

} else {
CWbuttonState = 0;
}

//Anti-Clockwise Push-button code
ACWbuttonState = digitalRead(ACWbuttonPin);

// check if the pushbutton is pressed. If it is, the buttonState is HIGH:
if (ACWbuttonState == HIGH) {

myStepper.step(-stepsPerRevolution);//Rotate anti-clockwise

} else {
ACWbuttonState = 0;
}

}