onOpen.gs

function onInstall(e) {
  onOpen();
}

function onOpen(e) {
  SpreadsheetApp.getUi().createAddonMenu()
    .addItem("Show Sidebar", "doGet")
  .addToUi();
};

function doGet(e) {
  var html = HtmlService.createTemplateFromFile('Sidebar')
    .evaluate();

  html
    .setTitle('Portfolio')
    .setWidth(300);
    
  SpreadsheetApp.getUi() // Or DocumentApp or SlidesApp or FormApp.     
    .showSidebar(html);
}

function showPicker() {
  const html = HtmlService.createHtmlOutputFromFile('Picker.html')
    .setWidth(1051)
    .setHeight(650)
    .setTitle('Pick a form to import to Portfolio');
  SpreadsheetApp.getUi().showModalDialog(html, 'Pick a form to import to Portfolio');
}

function include(filename) {
  return HtmlService.createHtmlOutputFromFile(filename)
      .getContent();
}

function getOAuthToken() {
  DriveApp.getRootFolder();
  return ScriptApp.getOAuthToken();
}