materio-d8/web/modules/custom/materio_commerce/materio_commerce.module

<?php

function materio_commerce_form_alter(&$form, &$form_state, $form_id) {
  if ($form_id == 'commerce_checkout_flow_multistep_default') {
      if ($form["#step_id"] == "review") {
          $t="t";
        // $form['buttons']['continue']['#value'] = t('Desired Custom Text Here');
        $form['actions']['next']['#value'] = t('Place your order');
      }
  }
}

function materio_commerce_form_commerce_order_add_form_alter(&$form, &$form_state, $form_id) {
  $currentUser = \Drupal::currentUser();
  $roles = $currentUser->getRoles();
  if (in_array("admin", $roles)){
    $t="t";
    $form['type']['#default_value'] = 'materio_order_type';
    $form['type']['#disabled'] = true;

    $form['customer']['uid']['#selection_handler'] = 'default:user_by_email';
  }
}