The technician's page for the Sonicwall is a configuration page that is not shown on the main configuration GUI. This tutorial will outline how to get there. This step will work on the entire TZ SonicWall line.
**Caveat Router: There be dragons ahead.**
Although this page is great for doing things you usually couldn't do, some of these features can absolutely soft-brick the router. Make sure you know specifically what you're looking for and what effect the feature will have if you enable it. The last thing you want is to shut down a primary firewall during business hours.
Make sure you can access the normal configuration page on the SonicWall. It will usually be the Gateway IP (192.168.xx.1).
To access the hidden configuration page, append /diag.html to the end of the router's URL address. For example, if you type 192.168.5.1 into the URL bar then you're going to want to add the /diag.html to the end of it (192.168.5.1/diag.html).
Voila. You are now in the technician's page.