Delete and Load Funcions not working in ListBox Script UI

Hi Experts

its just very tiny tool for saving GREP Queries, previously @Manan Joshi  helped me in creating it , now i add a title using multi columns lisbox in script UI so every grep query to be saved with its own title!, i  try to change tha code , i succeeded only in modifying inserting and saving function but i stucked in the Load and Delete functions, i still learning javascript so i get stucked from time to time! , i apperciate any help to make those functions works and thanks in advance :

var w = new Window ("dialog");
var myList = w.add ("listbox", undefined, " ",
{numberOfColumns: 2, showHeaders: true, columnTitles: ["GREP Name", "GREP Formula"]});

//MyListSize
myList.maximumSize.height = 1000;
myList.maximumSize.width = 1000;
myList.minimumSize.width = 1000;

//GREP Name
var StaticaName = w.add("statictext", undefined,"GREP Name");
StaticaName.alignment = "Left";
var myname = w.add ("edittext");
myname.active = true;
myname.characters = 100;

//GREP Formula
var StaticaGREP = w.add("statictext", undefined,"GREP Formula");
var input = w.add ("edittext");
StaticaGREP.alignment = "Left";
input.active = false;
input.characters = 100;

//-----------------------------------------------------------------------------------//
//Buttons Group 1
//-----------------------------------------------------------------------------------//
var gqmButtonGroup1 = w.add ('group {orientation: "row"}');
gqmButtonGroup1.alignChildren = "fill";
//GQMButtonGroup1.alignment = "stack";
//------------------------------------------------------------------------------------//
var inserttxt = gqmButtonGroup1.add ("button", undefined, " Insert GREP Query", {name: "Insert"});
var del = gqmButtonGroup1.add ("button", undefined, " Delete GREP Query", {name: "Delete"});
var gqmButtonGroup2 = w.add ('group {orientation: "row"}');
gqmButtonGroup2.alignChildren = "fill";
//GQMButtonGroup2.alignment = "stack";
var load = gqmButtonGroup2.add ("button", undefined, " Load GREP Queries", {name: "Load"});
var savelist = gqmButtonGroup2.add ("button", undefined, " Save GREP Queries", {name: "Save"});

//insert item Button
inserttxt.onClick = function () {
    insert_item (myList, myname.text);
    //insert_item (myList, input.text);
    input.text = "";
    input.text = "";
    input.active = true;
}

//delete selected item
del.onClick = function () {  
    // remember which line is selected
    var sel = myList.selection[0].index;
    for (var i = myList.selection.length-1; i > -1; i--)
    myList.remove(myList.selection[i]);

    // select a line after deleting one or more items
    if (sel > myList.items.length-1)
    myList.selection = myList.items.length-1;
    else
    myList.selection = sel;
}

function insert_item (list_obj, new_item) {
    if (list_obj.find (new_item) == null) {
    var stop = list_obj.items.length;
    //w.add(myList);
    var i = 0;
    while (i < stop && new_item > list_obj.items[i].text)
    i++;
    with (list_obj.add ("item", new_item, i)){
        subItems[0].text = input.text;
        }
    }
}

//Saving the List in the Same path of Indesign file (must before Show Command)
savelist.onClick = function () {
    //Define path and file name
    var filePathMinusExtension = app.activeDocument.fullName.fsName.substr(0, app.activeDocument.fullName.fsName.lastIndexOf("."));
    var writeFile = File(filePathMinusExtension + "_GREP_Queries.txt");
    writeFile.encoding = 'UTF-8';
    writeFile.open('w');
	var content = ""
	for(var i = 0; i < myList.items.length; i++)
        content += myList.items[i].toString() +","+ myList.items[i].subItems[0].toString() + "\r"
    writeFile.write(content);
    writeFile.close();
    alert("Done, File Saved in Same InDesign Document Location", "Alert!");
}

//Load List Items and Show them
load.onClick = function () {
    //Remove old list items
    myList.removeAll()
    var filePathMinusExtension = app.activeDocument.fullName.fsName.substr(0, app.activeDocument.fullName.fsName.lastIndexOf("."));
    var ReadFile = File(filePathMinusExtension + "_GREP_Queries.txt");
    if (ReadFile.exists) {
        try {
            ReadFile.open("r");

            while (ln = ReadFile.readln()) {
                myList.add("item", ln);
            }
            //Close the file
            ReadFile.close();
            alert("Done, the GREP Queries Loaded");
            return true;
        }
        catch (errOpen) {
            alert("Error. The GREP Queries file could not be opened!");
            return false;
        }
    }
    else{
        alert("The GREP Queries file could not be found!");
        return false;
    }
}

w.show ();