Hey Tony,
Well, what you're saying is fairly close to what I have setup.
I did indeed make root.com a Virtual Server -- and I setup phpMyAdmin within it (amongst some others).
But no other domains are sub-servers of it.
So, let's say I go to create a new Virtual Server (test.com) -- I set it up to create a DNS CNAME for phpmyadmin.test.com (which I configured in the DNS Server Template).
At that point, if I were to browse to phpmyadmin.test.com, since it's not currently aliased to any Virtual Host, I'd end up viewing the default Virtual Host, which I setup to be root.com (to make it the default, it just has to be the first Virtual Host listed in the Apache config).
Then, I edited the Apache Virtual Host config for root.com, and added this:
RewriteCond %{HTTP_HOST} ^phpmyadmin..*$ [NC]
RewriteRule ^(.*)
https://root.com/phpmyadmin/That says that anytime a URL beginning with "phpmyadmin." is seen, to redirect to "https://root.com/phpmyadmin".
And that's it -- now, anytime a new Virtual Server is added -- it creates a DNS CNAME for phpmyadmin, and whenever they go to it, it redirects to the central phpMyAdmin install in root.com.
-Eric