First off, my personal preference here is to have one central install of phpMyAdmin, and just include some sort of domain alias within each Virtual Server that redirects to the central install.
That allows you to have one commercial SSL certificate on your server, and makes keeping phpMyAdmin up to date a little easier.
That said, if you want to include any script available in the "Install Scripts" in every Virtual Server, go into System Settings -> Server Templates -> Default Template -> Default Script Installers, and add in the ones you wish to have installed by default.
-Eric
For one global install of phpmyadmin and each newly created virtual host having access, its really pretty simple.
Install phpmyadmin someplace, anyplace. Leave it in /usr/local/ or put it in /var/www/html, whatever. Configure phpMyAdmin.
Assuming you install phpMyAdmin in /var/www/html/phpMyAdmin, add the following to /etc/httpd/conf/httpd.conf in section 2.
Alias /phpMyAdmin "/var/www/html/phpMyAdmin"
Alias /phpmyadmin "/var/www/html/phpMyAdmin"
Restart apache. That’s it.
Now using a URL like so: http://www.host1.com/phpmyadmin
or http://www.host99.com/phpMyAdmin
will get you to phpmyadmin. As long as you didn’t create different database admin and virtualmin admin names/passwords, then your databases (and only yours) will be visible.