Until now, importing from an .atl or .xml file into DS has always been an all-or-nothing concept; it was not possible to import part of the file only. With the nasty side-effect of potentially corrupting your local repository by overwriting existing content by importing objects with the same name (and different functionality) as existing ones. There was no user-friendly interface for browsing the contents of an import file.
This has all changed in SP6!
Select Import from File... from the Tools menu, specify the file name, ignore the warning and you now get the Import Plan:
You can selectively exclude objects from the import. You can even exclude complete objects hierarchies at once. Just right-click and select the option from the pop-up menu, or click and select the right button from the bottom of teh screen.