No you aren't missing something.  Because you design it in MS Word, QuickBooks cannot edit the template.  Once you import it, thats how it is.  What you would need to do is open the word document of your template, make any changes you want, and then reimport the template.

You shouldn't have to start the template all over again because you have the saved MS Word document that you imported.  Just edit that document and save it as Template2.doc and import that one.  This way you have a list of different versions of your template you can always go back and reference.