Configuring the parent directory is located at /etc/psa/psa.conf and is set by DUMP_D.
# cat /etc/psa/psa.conf | grep -w DUMP_D
DUMP_D /var/lib/psa/dumps
To change the default backup server path, follow these steps:
Step 1: Create a folder that containing the backup:
mkdir /plesk_backups
Step 2: Open the /etc/psa/psa.conf file
Change the value of DUMP_D created at step 1 /plesk_backups to
DUMP_D /plesk_backups
Step 3: Permissions for /plesk_backups:
chown username.username /plesk_backups
Step 4: Restart sw-cp-server service
/etc/init.d/sw-cp-server restart
Now configure the backup path to be stored in the /plesk_backup directory
Good luck!