Editor <=> File
is simpler than: Editor <=> Copy/Paste Text Box/Save Button <=> File
It's a more cumbersome feedback loop while making changes.It's well-maintained and allows a user to inject custom CSS or JS on any URL, domain or all sites for their own tweaks and purposes. Maintaining these overrides just one click away offers a much better experience than hunting down this Custom.css buried within the filesystem.
Get the Chrome profile folder for your platform from: http://www.chromium.org/user-experience/user-data-directory (note, may not be "Default" if you use a created user profile.)
Get the extension number from chrome://extensions/
One thing that needs to be taken care of is updates-gone-rogue (a la HoverZoom, for example.)
There are dozens of extensions which change the new tab page - I didn't like any of them, so I hacked a quick one myself - it took me 2h? 1.5h? It was fast and I didn't need any complicated features - just a CSS-styled table with fixed list of links and a clock.
Here are some templates: https://github.com/bsilvereagle/Extensions
It's pretty straight foward in my opinion.