I tried as you discribed.
I used a html editorI only and changed one word in the content of the original help_en_US.html
document an I leaved the name of the file unchanged, it does not work
. Changed document is not accepted.
When I use a new html document (with other content) and give it the name help_en_US.html
it is accepted. But when I open Help in OCPN not the new content is opened but automaticaly help_web.html
from the Netherlands