Clicking On View Post In Draft Opens New Tab

You can hack by adding below lines in your theme’s functions.php file.

function remove_preview_target()
{
    // below JS code will set Preview button's **target** attribute to **_self**, it means same tab/window.
    echo "<script>
        jQuery(document).ready(function(){
        jQuery('#post-preview').attr('target', '_self');
        })
        </script>";

}
// this action performs in admit footer
add_action('admin_footer', 'remove_preview_target');

Or add below lines in your JS file.

jQuery(document) . ready(function () {
     jQuery("#post-preview") . attr("target", "_self");
});