code: private function writeWindow1()
      {
          $record = 0x003D; // Record identifier
          $length = 0x0012; // Number of bytes to follow
  
          $xWn = 0x0000; // Horizontal position of window
          $yWn = 0x0000; // Vertical position of window
          $dxWn = 0x25BC; // Width of window
          $dyWn = 0x1572; // Height of window
  
          $grbit = 0x0038; // Option flags
  
          // not supported by PhpSpreadsheet, so there is only one selected sheet, the active
          $ctabsel = 1; // Number of workbook tabs selected
  
          $wTabRatio = 0x0258; // Tab to scrollbar ratio
  
          // not supported by PhpSpreadsheet, set to 0
          $itabFirst = 0; // 1st displayed worksheet
          $itabCur = $this->spreadsheet->getActiveSheetIndex(); // Active worksheet
  
          $header = pack('vv', $record, $length);
          $data = pack('vvvvvvvvv', $xWn, $yWn, $dxWn, $dyWn, $grbit, $itabCur, $itabFirst, $ctabsel, $wTabRatio);
          $this->append($header . $data);
      }
docs: Write Excel BIFF WINDOW1 record.