does 0.11.0 works well for you?

It'll be support with next release.
https://github.com/rhiokim/haroopad/issues/283

You can customize "editing area" & "viewer" using css.

1. Exec haroopad
2. Open preference window
3. Click editor tab or viewer tab
4. Click edit button in 'Your style' section
5. Edit your style & Import your local font using css
6. Save to your css file. e.g) MyStyle.css
7. Click reload button
8. Select your style.

You can customize "editing area" & "viewer" using css.

1. Exec haroopad
2. Open preference window
3. Click editor tab or viewer tab
4. Click edit button in 'Your style' section
5. Edit your style & Import your local font using css
6. Save to your css file.  e.g) MyStyle.css
7. Click reload button
8. Select your style.

Thanks. :-)