Create a Custom Menu with Apps Script

Google Sheets allows you to quite simply create custom menus, such as:

Simple Menu

In this example, the onOpen function adds the new menu upon opening the document:

function onOpen() {
  SpreadsheetApp.getUi()
    .createMenu('Sheets-Pratique')
    .addItem('Example 1', 'example1')
    .addItem('Example 2', 'example2')
    .addToUi();
}

function example1() {
  Browser.msgBox('Easy!');
}

function example2() {
  Browser.msgBox('Nice!');
}

If Example 1 is clicked, the example1 function will be executed (the principle is the same for Example 2 and the example2 function):

Separators

If needed, you can add separators to better distinguish groups:

function onOpen() {
  SpreadsheetApp.getUi()
    .createMenu('Sheets-Pratique')
    .addItem('Example 1', 'example1')
    .addItem('Example 2', 'example2')
    .addItem('Example 3', 'example3')
    .addSeparator()
    .addItem('Test 1', 'test1')
    .addItem('Test 2', 'test2')
    .addToUi();
}

Sub-menus

It is also possible to add sub-menus:

function onOpen() {
  const ui = SpreadsheetApp.getUi();
  ui.createMenu('Sheets-Pratique')
    .addItem('Example 1', 'example1')
    .addSubMenu(ui.createMenu('Example 2')
      .addItem('Test 1', 'example2.test1')
      .addItem('Test 2', 'example2.test2')
      .addItem('Test 3', 'example2.test3'))
    .addItem('Example 3', 'example3')
    .addToUi();
}

For example, the functions of the sub-menu have been grouped in the example2 object:

const example2 = {
  test1: function() {
    Browser.msgBox('Clicked on "Test 1"!');
  },
  test2: function() {
    Browser.msgBox('Clicked on "Test 2"!');
  },
  test3: function() {
    Browser.msgBox('Clicked on "Test 3"!');
  }
}

function example1() {
  Browser.msgBox('Clicked on "Example 1"!');
}

function example3() {
  Browser.msgBox('Clicked on "Example 3"!');
}