I'm evaluating the use of BizTalk 2004 as the underpinnings for v.next of a project, and as I ramp up on this vast and powerful suite of tools have been struggling mightily to work within the constraints the BizTalk schema editor.
It's nice, I guess, that there's tooling that lets you work with an XSD schema as a tree view made up of nodes that are exposed as properties; but sometimes you just want to edit the [expletive deleted] file the old-fashioned way, or maybe do a global search and replace on it. But when you install BizTalk 2004 it assigns its own Schema editor to XSD files.
Turns out it is possible to overcome this feature (thanks to Stephen Kaufman for documenting it here).
In Visual Studio's Solution Explorer right click the XSD file you want to edit, choose "Open With," and select "Xml Schema Editor." Viola! Now you have line numbers and regex search and replace and all those other indespensible goodies.