In Microsoft's recent release of Expression Web 3, they decided not to include add-in support. They may decide to issue an upgrade to EW3 for add-in support. With that in mind our development for Expression Web products is currently on hold.
Expression Web and Dreamweaver do not share the same template architecture, a template created in cannot be used a s a template in the other.
You would be able to make the Dreamweaver Template in Expression Web, but not apply those changes to the child pages. That could only be done in Dreamweaver. It would be best to stick to one editing environment instead of switching back and forth.
