Controlling stepper motors via serial monitor - AccelStepper library

Why not do something simple and obvious like this

void loop()
{
     
    if(Serial.available()>0) // If any information is avaiable coming from the serial monitor
    {
        inBuffer = Serial.read(); // Puts the information coming from the serial monitor in the input buffer
    }
        
    if (inBuffer == 'a') // If the command sent is an 'a'
    {
        Serial.println("test point 1"); //Serial print for test point 1
        
     
        if (stepper1.distanceToGo() == 0) {
            if (stepper1.currentPosition() == 0) {
                stepper1.moveTo(movement);
            }
            else {
                stepper1.moveTo(0);
            }
        }
        
        if (stepper2.distanceToGo() == 0) {
            if (stepper2.currentPosition() == 0) {
                stepper2.moveTo(movement);
            }
            else {
                stepper2.moveTo(0);
            }
        }
        inBuffer = ""; // clear this immediately the 'a' has been used

    }

    stepper1.run();
    stepper2.run();

}

...R