Hi Joohmla,
You can add the following JS to the Dashboard > Systems > Site template styles > Select template > Global Settings > Custom Code > Before</body>
<script>
jQuery(document).ready(function($) {
$('.target-blank .btn').attr('target', '_blank');
});
</script>
To add target="blank"_ to a button, open the desired module, go to the Advanced tab, and enter the target-blank class in the Module Class field.