Xcode Source Editor Extension invoking existing menu item

Question

The source editor extensions look good but it seems you can only manipulate the text in the source file and nothing else. Am I missing something or can you somehow invoke an existing editor menu command (such as code indent, show invisibles etc?). I'm looking for a way to fold / unfold code and use the existing refactoring menu commands in my extension but can't find any way to invoke them. I find it odd as one may create an extension that calls another (just as apps use other app extensions as editors / processors).