When I insert the navigation, I cannot see it in Design view of Dreamweaver CS6. I can see it in Source Code view and it appears to be working, but I cannot see it in Design view.

Hi Bart,
Could you please provide a link to the page that is not being rendered well in design view so i can check the source code?

beta.ntechwebs.com/bootstrap.php
renders fine int he browser, just not Dreamweaver

Hello Bart, please update your Bootstrap 3 extension to the latest version.

Makes no difference.
If I add NAV, I can see it. If I add NAVBAR, I cannot. I can see it in Code View and the browser, but not Design View. It does appear in Live View.

Hi Bart,
The css and js files of the bootstrap you are using are still an old version: Bootstrap v3.0.3 should be Bootstrap v3.1.1
Please update them:

<link rel="stylesheet" type="text/css" href="bootstrap/3/css/bootstrap.css" />
...
<script type="text/javascript" src="bootstrap/3/js/bootstrap.js"></script>

Thanks. That resolved it.