If you want to customize the configs of a specific domain oder subdomain, you can create a file in the ./conf directory named “vhost.conf”.
It’s contents will be integrated in the config by Plesk after you change the domain-configuration.

To manually trigger this, you can run:

/<path_to_plesk>/admin/sbin/websrvmng --reconfigure-vhost --vhost-name=<domainname>

For an ubuntu-machine (with Plesk 9) this comes down to:

/opt/psa/admin/sbin/websrvmng --reconfigure-vhost --vhost-name=<domainname>