Userscript for Tampermonkey to intercept F1 on Google Sheets, so that the annoying Help popup can be suppressed.

GoogleSheetsDisableF1.js

// ==UserScript==
// @name         F1 key interception on Google Sheets to suppress the Help
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Interception of F1 keypress on Google Sheets and replaces default behavior with nothing.

// @author       Flemming Steffensen
// @match        https://docs.google.com/spreadsheets/*
// @grant        none
// ==/UserScript==

document.addEventListener("keydown", function(event) {
  // For typical shortcuts
  //    Windows & Linux use the Control key == ctrlKey
  //    Mac uses the Command key == metaKey
  //    Other group keys are altKey and shiftKey
  var isMac = navigator.platform.toUpperCase().indexOf('MAC')>=0;
  var modifier = isMac ? event.metaKey : event.ctrlKey;

  var debug = false
  if(debug) {
    if (!( (event.code === "ControlLeft") || (event.code === "ControlRight")
        || (event.code === "MetaLeft") || (event.code === "MetaRight")
        || (event.code === "AltLeft") || (event.code === "AltRight")
        || (event.code === "ShiftLeft") || (event.code === "ShiftRight")
        )) {
      alert("Key pressed Pressed: " + event.code + " (" + event.keyCode + ") on " + (isMac ? "Mac" : "nonMac ") + (modifier ? "with" : " without") + " modifier." )
    }
  }

  // For some reason this triggers on F1, but not shift-F1, although event.code is F1 for both.
  if (event.code === "F1") {
    event.preventDefault();
  }

});