How to add item to Dart Flutter Secure Storage stringList?

Question

My goal is to save a list with Secure Storage and add new items to this list. There will be a list. There will be items in it. I want to add an item to that list later. In the methods I tried, it did delete the entire list. I couldn't add an item to the already existing list.

How can I do it?

I am currently stuck here:

    Future<void> listUpload() async {
    final prefences = await SharedPreferences.getInstance();
    prefences.setStringList("values", ["Value 1"]);
    var printList = prefences.getStringList("testler");
    debugPrint(printList.toString());
    setState() {
    
    }
  }