You can replace the navigation links at the top, and the disclaimer at the bottom, by adding a couple more environment variables:
DASHBOARD_HEADER_HTML: For example, put in
<a class="header-link" href="//example.com">My Home</a>(links use
atags, while the selected link, which is “Dashboard” in the default nav bar, uses a
btag with the same class)
DASHBOARD_FOOTER_HTML: For example, put in
This site is only for authorized employees of Example Inc.
On Heroku, you can go into the Settings tab under your app to add these env variables.