local_file_debugger.js

// ==UserScript==
// @name         Add Local Files to NetSuite SuiteScript Debugger
// @namespace    https://debugger.netsuite.com
// @version      0.1
// @description  This script adds a file input in the command toolbar of NetSuite's script debugger.  You can then add a local file to the text area to debug
// @author       S. Wilson.
// @match        https://debugger.netsuite.com/app/common/scripting/scriptdebugger.nl?*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';

    window.loadExternalFile = function() {
        var file = document.getElementById("myFile").files[0]; 
        var reader = new FileReader();
        reader.onload = function (e) { 
            var textArea = document.getElementById("mainscript");
            textArea.value += e.target.result; };
        reader.readAsText(file);
    };

    var x = document.getElementsByClassName('uir-header-buttons');
    var x0 = x[0];
    var tr = x0.firstChild.nextSibling.firstChild.nextSibling.firstChild;
    var td0 = document.createElement('td');
    td0.innerHTML ='<input id="myFile" onchange="loadExternalFile();" type="file">';
    tr.append(td0);


})();