Add a toggle collapse to enable one click collapse/expand.

Phabricator-toggle-collapse.js

const mouseEvent = document.createEvent('MouseEvents')
mouseEvent.initEvent('click', true, true)
const COLLAPSE_FILE = 'Hide Changeset'
const EXPAND_FILE = 'Expand File'

const getOptionsButton = (element) => {
  const links = [...element.getElementsByTagName('a')].filter(link => link.innerHTML.search('View Options') > -1)
  if (links.length <= 0) {
    throw new Error('Now Option Button Found!')
  }
  return links[0]
}

const filterButton = (dropdownButtons, target) => {
  const buttons = dropdownButtons.filter(({ innerHTML }) => innerHTML.includes(target))
  if (buttons.length) {
    return buttons[0]
  }
}

const getToggleButton = (element) => {
  const dropdownButtons = [...document.getElementsByClassName('phuix-dropdown-menu')[0].getElementsByTagName('a')]
  return {
    collapse: filterButton(dropdownButtons, COLLAPSE_FILE),
    expand: filterButton(dropdownButtons, EXPAND_FILE)
  }
}

const getClickFunc = (element, button) => () => {
  const optionButton = getOptionsButton(element)
  optionButton.dispatchEvent(mouseEvent)
  const { collapse, expand } = getToggleButton()
  console.log({ collapse, expand })
  if (!collapse && !expand) {
    return optionButton.dispatchEvent(mouseEvent)
  }
  (collapse || expand).dispatchEvent(mouseEvent)
  button.innerHTML = collapse ? EXPAND_FILE : COLLAPSE_FILE
}

const getButton = (element) => {
  const button = document.createElement('button')
  button.innerHTML = COLLAPSE_FILE
  button.addEventListener('click', getClickFunc(element, button))
  return button
}

const insertButtons = () => {
  [...document.getElementsByClassName('differential-changeset-buttons')].map((element) => {
    element.insertAdjacentElement('afterbegin', getButton(element))
  })
}

insertButtons()