Compared to a cPanel environment, where you are almost exclusively required to use a .htaccess file, in Plesk you are able to reconfigure Apache and add to the configuration file on the fly.
In every domain and sub domain created in Plesk there is a folder named "conf" that contains a file named "httpd.include" which contains the automatically generated Apache configuration created by Plesk. Since you don't want to edit an automatically generated file, Plesk includes a way to add-on to the httpd.include via the "vhost.conf" file. In the same "conf" folder, create a new file named "vhost.conf". I typically do this by typing in the following into the command line:
I then add my Apache configurations to the vhost.conf file and then save them by typing in:
Now you'll need to tell Plesk to reload it's Apache configuration by typing in the following (replace example.com with your domain name):
/usr/local/psa/admin/sbin/websrvmng -u --vhost-name=example.com