Perform an action after each step in a multi-step Webform

I'm trying to figure out how to grab data from the previous step of a multi-step webform after a user progresses and I'm coming up blank.

Is there a particular hook that gets fired whenever a users progresses forward in a multi-step form or do I need to add a custom submit handler?

Thank you!

I was able to get this working.

In my hook_form_alter() function I had to add a custom submit handler to the wizard_next action:

function my_module_form_alter(&$form, FormStateInterface $form_state, $form_id) {
    if($form_id == 'my_form') {
        $form['actions']['wizard_next']['#submit'][] = 'my_module_custom_submit';
    }
  }

function my_module_custom_submit(array $form, \Drupal\Core\Form\FormStateInterface $form_state) {
 // Custom submit behavior
}