That is exactly what I have done! But what do I do if, for level 4, I chose level 3 in the "Include level number from," and it only inserts one digit?

Look at the screenshot in my previous post, and you'll see only one digit in the "Enter formatting for number" field. This is what I get when I choose level 3 in the "Include level number from."

Isn't this happening on your computer? When you choose level four, does it insert 1.1.1? Is the problem somehow with my computer?

I assume by "click on any paragraph with the 1Appen Style," you mean I only have to do this once and then format all levels. Not open and close the box for each level.