When you mount SFTP drive, you can use specific path as a mount point.
If you selected ‘Connect to user home folder’:
Set URL as following format:
sftp://address:port/<path_under_home_folder>
If you want to mount ~/document, specify the URL like:
sftp://address:port/document
If you selected ‘Connect to system root folder’, specify the URL like following to mount /var/log.
sftp://address:port/var/log