The setting in the module doesn’t work.

Source: https://www.elegantthemes.com/blog/divi-resources/how-to-open-fullwidth-header-slider-buttons-in-new-tabwindow

Add the following in a code module on the page, or side wide in the theme options » integration » head.

<script>
jQuery(function($){
$('.et_pb_fullwidth_header_0 .header-content-container .header-content .et_pb_button_one.et_pb_button').attr('target', '_blank');
$('.et_pb_fullwidth_header_0 .header-content-container .header-content .et_pb_button_two.et_pb_button').attr('target', '_blank');
});
</script>Code language: HTML, XML (xml)