Visual form builder: how to add a default value?

I have created a form using visual form builder plugin. I want to set a default value for a field from url.

I wrote the following code for this.

add_filter( 'vfb_field_default', 'cs_vfb_filter_field_default', 10, 4 );
function cs_vfb_filter_field_default($default, $field_type, $field_id, $form_id) {
 if($field_id == 42 && $form_id == 3) {
                return $default = 'some text';
        }

}

But it is not working? Any one who have some idea about this?

https://wordpress.org/plugins/visual-form-builder/