Sorry for the delay, I just noticed your post
This relates to editing the underlying html code for a note
Every note has an enml component that defines the note formatting
On a Mac, this is stored as a separate file for each note named content.enml
This is basically html code; documented at https://dev.evernote.com/doc/articles/enml.php
Locate the file (I use a script), and edit with a text editor app
Simple changes can be made to fine tune formatting, however Evernote may override more complex code