I was unsuccessful in doing what you want to do but I came up with a
great work around. I created a static HTML file that pointed to the
category and then I created a sub-dashboard that pointed to the HTML file.
This also worked great for me to allow categories from different workspaces
to all be at the same location.

I finally had some time to figure this one out. It was so simple.
Create a sub-dashboard, for example - Test. In IIS, setup a redirect
on the Test sub-dashboard to the desired category.