Class Menu

// Add a custom menu to the active spreadsheet, including a separator and a sub-menu.
function onOpen(e) {
  SpreadsheetApp.getUi()
      .createMenu('My Menu')
      .addItem('My Menu Item', 'myFunction')
      .addSeparator()
      .addSubMenu(SpreadsheetApp.getUi().createMenu('My Submenu')
          .addItem('One Submenu Item', 'mySecondFunction')
          .addItem('Another Submenu Item', 'myThirdFunction'))
      .addToUi();
}