When I write Markdown text and use the formatting for headlines, bold and italic, it changes inside the editor.
Both the Markdown and the Rich Text Editor have some kind of formatting that's not consistent.
It it possible to completely turn off formatting so I can just concentrate of writing markdown code for the notes?
Different spacing and line width jumping around while typing make editing very confusing, when you're used to write just Markdown in other software.
Below a screenshot on how my editor window looks.
I'd prefer to see everything in one font size and not have any specific style applied.
After adding your code to userchrome.css the markdown editor windows behaviour didn't change for me. It still applies the formatting from markdown to the text in the markdown editor (which should not have any formatting at all)
I tried restarting Joplin after the change and verified that the userchrome.css now has this content.