As far as I know, the only way to not have a horizontal scroll bar (other than making sure all of your text has short lines) would be to turn on the word wrap feature with a wrap width of 0 to make it wrap at the edge of the window.
This changes what you see in the window though which may or may not be desirable. If that’s not a problem, you can do something like:
- Open a markdown file
- Select
Preferences > Settings - More > Syntax Specific - User
- Enter something like the below in the file
{
"word_wrap": "true",
"wrap_width": "0"
}
That will apply word wrapping always at the edge of the window specifically for markdown files while leaving everything else alone.