i am using adminlte theme and datatables buttons but i want to export excel with multiple table head ex:- shown in below
i have try so many references but i could not get a solution.

this is html table.

<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Source+Sans+Pro:300,400,400i,700&display=fallback">

<link rel="stylesheet" href="~/V3/plugins/fontawesome-free/css/all.min.css">

<link rel="stylesheet" href="~/V3/plugins/datatables-bs4/css/dataTables.bootstrap4.min.css">
<link rel="stylesheet" href="~/V3/plugins/datatables-responsive/css/responsive.bootstrap4.min.css">
<link rel="stylesheet" href="~/V3/plugins/datatables-buttons/css/buttons.bootstrap4.min.css">
<link rel="stylesheet" href="https://cdn.datatables.net/fixedheader/3.1.9/css/fixedHeader.dataTables.min.css">

>

            <table id="example1" class="table table-bordered table-striped">
              <thead>
              <tr>
                <th colspan="2">Rendering engine</th>

                <th colspan="3">CSS grade</th>
              </tr>
              <tr>
                <th>engine</th>
                <th>1Browser</th>
                <th>2Platform(s)</th>
                <th>3Engine version</th>
                <th>4CSS grade</th>
              </tr>
              </thead>
              <tbody>
              <tr>
                <td>Trident</td>
                <td>Internet
                  Explorer 4.0
                </td>
                <td>Win 95+</td>
                <td> 4</td>
                <td>X</td>
              </tr>
              <tr>
                <td>Trident</td>
                <td>Internet
                  Explorer 5.0
                </td>
                <td>Win 95+</td>
                <td>5</td>
                <td>C</td>
              </tr>
              <tr>
                <td>Trident</td>
                <td>Internet
                  Explorer 5.5
                </td>
                <td>Win 95+</td>
                <td>5.5</td>
                <td>A</td>
              </tr>
              </tbody>
            </table>

In ouput:

$(document).ready(function () { $("#exampleN").DataTable({ "responsive": false, "lengthChange": false, "autoWidth": false, "aLengthMenu": [[100, 120, 150, -1], [100, 120, 150, "All"]], "paging": false, autoFilter: true, dom: 'Bfrtip', buttons: [ { extend: 'copyHtml5', title: function () { return row1; }, orientation: 'landscape', pageSize: 'LEGAL', text: 'Copy', titleAttr: 'COPY' }, { extend: 'excelHtml5', title: function () { return "Driver Information Report"; }, orientation: 'landscape', pageSize: 'LEGAL', text: 'Excel', titleAttr: 'EXCEL' }, { extend: 'csvHtml5', title: function () { return "Driver Information Report"; }, orientation: 'landscape', pageSize: 'LEGAL', text: 'CSV', titleAttr: 'CSV' }, { extend: 'pdfHtml5', title: function () { return "Driver Information Report"; }, orientation: 'landscape', pageSize: 'LEGAL', text: 'PDF', titleAttr: 'PDF' }, { extend: 'print', title: function () { return "Driver Information Report"; }, orientation: 'landscape', pageSize: 'LEGAL', text: 'Print', titleAttr: 'PRINT' } ] }).buttons().container().appendTo('#exampleN_wrapper .col-md-6:eq(0)'); });