Edit issues

Hello

I would like to create an html file in my WordPress site root folder using File Manager. When I create a blank file and try to access any of the editing options available on right-clicking the file, I receive the response “Invalid backend response.
Data is not JSON.” I have confirmed that this not unique to html files, as the same response occured with a .txt file. Can you please assist me in finding how to resolve this problem. I want to create the file within my WordPress site rather than upload it.

Many thanks in advance!