www.wysiwygwebbuilder.com

Needed:
On "Page HTML", add tab: "After </body> tag"

Why:
So this script can be used:
https://github.com/jadeallencook/gDoc.js which requires:
</body>
<footer>
<script>
gDoc(yourPublicId, sheetName);
</script>
</footer>
</html>

What is it for:
Supposedly, you can use the script on the mentioned github.com page to allow a client to edit a Google Docs spreadsheet, and include it in your page. Using the Google Docs embed method has issues, and it would appear this gDoc.js might clear them up.

FYI
Just looking for the SIMPLEST method to allow several clients who are really wanting to update some pages of their sites on their own. CMS solutions are too complicated (???), but they use can Google Docs...

The code must be placed between the body tags. If you the footer after the body tag, it will result in invalid HTML code.

https://www.w3schools.com/tags/tag_footer.asp

On "Page HTML", add tab: "After </body> tag"

As Pablos reply then use move javascripts to the end of the page with 'Move JavaScript to the end of the page' in Tools->Options->HTML

Just looking for the SIMPLEST method to allow several clients who are really wanting to update some pages of their sites on their own. CMS solutions are too complicated

Then you will really need some kind of CMS! See the following
https://www.wysiwygwebbuilder.com/newswriterpro.html