How do I go about creating a browser like the System Browser?
The OmniBrowser framework [1] included in 3.9 or available from SqueakMap is targeted at building new browsers. There is a clone of the System Browser toolset included, but a lot of other 'quite' different browsers have been built around this framework. Certainly worth a try.
Cheers, Lukas
[1] http://www.wiresong.ca/OmniBrowser