Adding a link on the nested data table

I would like to add a download link, just before search box. I am using third level nested data table. This data creates dynamically on AJAX respond data.
I am using the following plugins;
Datatable
nested data table

 Second and third level of table is shown, when user click on the table rows. How I can add download link for the last level of the datatable ?

 var appendDownloadLink = $(".dataTables_filter");
    		                    
appendDownloadLink.prepend('<a class="download">Download</a>');

Select allOpen in new window

JSfiddle