Nothing in SysInfo for this.
The line should look like:
sftp://user_name@domainname.com:xxxx/
were xxxx is the used port number, default is 22, but you surely make your server safer by not using that, but a random number 🙂
You're server might need fish:
fish://user_name@domainname.com:xxxx/
You can add the above options directly in the address bar of Dolphin, only edit the side panel when you entered all correctly and server up/downloads work.