I have the following code for a Google Sheet which utilises a Utilities.sleep() call.
Problematically, both highlightChildren() and unhighlightChildren() are executed after the Utilities.sleep() call and I can't figure out why.
function onOpen() {
  var ui = SpreadsheetApp.getUi()
  ui.createMenu('OKRs').addItem('Show linked Key Results', 'getLinkedKeyResults').addToUi()
}
var highlightChildren = function(rangeList) {
  SpreadsheetApp.getActiveSpreadsheet().getActiveSheet().getRangeList(rangeList).setBackground('#ffd966')
}
var unhighlightChildren = function(rangeList) {
  SpreadsheetApp.getActiveSpreadsheet().getActiveSheet().getRangeList(rangeList).setBackground('#ffffff')
}
function extendChildrenRefs(stringRefs) {
  return stringRefs.replace(/C/gi, 'B') + ',' + stringRefs
}
function getLinkedKeyResults() {
  var scriptProperties = PropertiesService.getScriptProperties()
  var ss = SpreadsheetApp.getActiveSpreadsheet()
  var parentRef = ss.getActiveCell().getA1Notation()
  var children = extendChildrenRefs(scriptProperties.getProperty(parentRef)).split(',')
  highlightChildren(children)
  Utilities.sleep(4 * 1000)
  unhighlightChildren(children)
}
/**
 * Links a parent key result progress to child key results, storing them in memory. Otheriwse, a direct clone of AVERAGE().
 *
 * @param {"value1, value2, value3..."} values The child key result values to consider when calculating parent key result progress.
 * @return The average of range of value.
 * @customfunction
 */
function LINKKEYRESULTS(values) {
  if (arguments.length < 2) throw new Error('You must pass at least two key result values!')
  var ss = SpreadsheetApp
  var scriptProperties = PropertiesService.getScriptProperties()
  var formula = ss.getActiveRange().getFormula()
  var args = formula.match(/=\w+\((.*)\)/i)
  var parentRef = ss.getActiveRange().getA1Notation()
  var childrenRefs = args[1]
  scriptProperties.setProperty(parentRef, childrenRefs)
  var children = childrenRefs.split(',')
  var sum = 0
  children.forEach( function(child) {
    sum += ss.getActiveSheet().getRange(child).getValue()
  })
  return sum / children.length
}
The following GIF shows the buggy behaviour. Note that I commented out the unhighlightChildren method call in order to show the buggy behaviour. If I leave it in you wouldn't see the highlight, since after 4 seconds the highlight is triggered but is immediately followed by unhighlight, which makes it appear as if neither method is called (which is not true):
