ResolutionThis feature is planned to be implemented in the future Plesk versions. This time it can only be done manually.
Login to the server as 'root' user and create a system user (for example USER_NAME) with home directory you need, for example:
# /usr/sbin/useradd -d $HTTPD_VHOSTS_D/your_domain/some/location -s /bin/false USER_NAME
Set the password for this user using 'passwd' command.
Add this user into 'psacln' group:
# /usr/sbin/usermod -G psacln USER_NAME
The user will be 'chroot'-ed to his home because 'psacln' group is listed in /etc/ftpchroot. Set read/write permissions for this user on his home directory, for example:
# chmod 755 $HTTPD_VHOSTS_D/your_domain/some/location
# chown USER_NAME:psacln $HTTPD_VHOSTS_D/your_domain/some/location
And set execute permission on the domain's httpdocs folder:
# chmod 751 $HTTPD_VHOSTS_D/your_domain/httpdocs
$HTTPD_VHOSTS_D - have to be replaced with the real path to the Plesk virtual hosts in the all examples above.