Making a copy/clone of a "List<List<Map>>"

Question

I'm trying to create a copy/clone of a "List<List<Map'>>".

So far I tried:

dataFTY2 = dataFTY.map((element)=>element).toList();
dataFTY2 = json.decode(json.encode(dataFTY));
dataFTY2 = List.from(dataFTY);

Nothing seems to work. Whenever I change the copy "dataFTY2", dataFTY changes as well. I need this to be a completely independent copy. Please help. I cant seem to figure this out, its driving me crazy.

More code added for reference.

List failureDetails = [];
    List trackIDs = [];
    List dateTime = [];
    var dataFTY2 = dataFTY.map((element) => element.map((ele) => Map.from(ele)).toList()).toList();

    // get historyData for each one and sort through "F"s and put them into the table in a row?
    for (var x in dataFTY2[4]) {
      trackIDs.add(x["track_id"]);
      dateTime.add(x["datetime"]);
    }
    List failuresOnly = List.filled(trackIDs.length, {}, growable: true);
    for (var i = 0; i < trackIDs.length; i++) {
      await fetchTrackIDTestDetails(context, trackIDs[i], dateTime[i], false);
      failureDetails.add(MyGlobals().getTestCodeDetailsData());
    }
    //filter out only "F"s
    for (var p = 0; p < failureDetails.length; p++) {
      for (var t in failureDetails[p][0]) {
        if (t["Status"] == "F") {
          //add it to list, if pass do nothing
          failuresOnly[p] = t;
        }
      }
    }
    //combine with FTY failure data, don't use new screen use old screen and toggle when pressed, add column on right side
    //dataFTY2 = MyGlobals().getFTYFailureMoreDetails();
    for (var i = 0; i < dataFTY2[4].length; i++) {
      dataFTY2[4][i]["TestCode"] = failuresOnly[i]["TestCode"];
      dataFTY2[4][i]["Status"] = failuresOnly[i]["Status"];
      dataFTY2[4][i]["TestValue"] = failuresOnly[i]["TestValue"];
      dataFTY2[4][i]["Lo_Limit"] = failuresOnly[i]["Lo_Limit"];
      dataFTY2[4][i]["Up_Limit"] = failuresOnly[i]["Up_Limit"];
      dataFTY2[4][i]["ProcTime"] = failuresOnly[i]["ProcTime"];
    }

Answer 1

You can use Map.from named constructor to clone the Map like this,

dataFTY2 = dataFTY.map((element) => element.map((ele) => Map.from(ele)).toList()).toList();