Google script to import CSV file to google sheet.

importCSV.js

function importCSVFiles()
{
  var ss = SpreadsheetApp.getActiveSpreadsheet(); 
  Logger.log(`Active Spreadsheet: ${ss.getName()}`);
  
  const rootFolderId = '1EDAXA7TbzCnzmczRMHD_LxoF0yopS5D2';                  // Root folder
  const csvFolderName = 'Data';                                              // Folder containing csv files and the Archive folder
  const archiveFolderId = '1clsKkp0bauYkbg0uQj8LfaHIQIrpJWO8';               // Archive Folder
  const destinationSheetName = 'final';                                      // destination sheet in spreadsheet
  
  const root = DriveApp.getFolderById(rootFolderId);
  Logger.log(`Root Folder: ${root.getName()}`);
  const archiveFolder = DriveApp.getFolderById(archiveFolderId);
  Logger.log(`Archive Folder: ${archiveFolder.getName()}`);
  
  const fileName =/ *.csv/;
  
  var rootFolders = root.getFolders();
  
  const sheet = ss.getSheetByName(destinationSheetName);
  Logger.log(`Sheet Name: ${sheet.getName()}`);
  
  var csvArray = [];
  
  while (rootFolders.hasNext()) 
  {
    var folder = rootFolders.next ();
    Logger.log(`folder.getName() ${folder.getName()}`);
    if (folder.getName() === csvFolderName) 
    {
      importCSV(folder);
    }
    else 
    {
      var csvFolder = folder.getFoldersByName(csvFolderName);
      while (csvFolder.hasNext()) 
      {
        importCSV(csvFolder.next());
      }
    }
  }
  
  function importCSV(folder) 
  {
    var files = folder.getFiles();
    while (files.hasNext()) 
    {
      var file = files.next();
      Logger.log(`file.getName() ${file.getName()}`);
      csvArray = file.getBlob().getDataAsString("UTF-8");
      csvArray = Utilities.parseCsv(csvArray.replaceAll(/"/g, '\\"'), ';');
      csvArray.shift();
      sheet.insertRowsAfter(1,csvArray.length);
      sheet.getRange (2,1,csvArray.length,csvArray[0].length).setValues(csvArray);
      
      file.moveTo(archiveFolder);
    }
  }
}

You are going to have to play around with the insert API's . This is all I know on this topic as this is the most that I needed. You already have the filename in line 48. So I guess you do another insert on line 55.

That's what I was playing around with. Maybe the answer will lie in the reference you linked. Thanks for the help!