Hello,

There is no auto generate for option for code. The code filed is used to generate barcode and it should be unique per product.

If you want to click the generate button automataically, you can add the following code at the end of themes/default/admin/views/products/add.php

<script>
$(document).ready(function () {
  $('#random_num').trigger('click');
});
</script>

Thank you