You can use Dreamweaver to create brand new outer page layouts for your Actinic store. These are also known as overall page layouts - see What Is An Overall Page Layout? for more details about these). This will then create new outer/overall layouts within Actinic that will be used by your store pages. You can still edit the files in Dreamweaver, and all changes will be instantly passed to Actinic.
The idea is that you can take designs that you have already created, and 'register' them within Actinic. Actinic will then make sure that design will work correctly, by making a few changes to the code in the <head> section. You will then be able to slot the required Actinic layout selectors in place to make the design work as an outer/overall page layout.
Then any change you make in Dreamweaver will be immediately visible in Actinic, and any change you make in Actinic will be immediately visible in Dreamweaver.
You can create and register any number of outer/overall layouts with the Dreamweaver plug-in.