customStep property

Defines a custom Widget to display at each step instead of a simple container, given the current step index, the Color of the step, which could be defined with selectedColor and unselectedColor or using customColor, and its size double, which could be defined using size, selectedSize, unselectedSize, or customSize. When progressDirection is TextDirection.rtl, the index count starts from the last step i.e. the right-most step in the indicator has index 0

customStep: (index, color, size) {
  return Container(
    color: color,
    child: Text('$index $size'),
  );
}

If you are not interested in the color and the size:

customStep: (index, _, __) {
  return Text('$index');
}

Implementation