you can just edit the settings.json file via whatever protocol you like using a text editor that supports unix-files. I use Notepad++ and edit the file over CIFS.
If you don't see the addons-config share, you can create a share for it and set permissions for whatever user you like. This might give Transmission permission-problems though. You can also find the directory on the c. You will have to log in (using CIFS) as admin and go to \\ipofnas\c\addons-config\Transmission\transmission-daemon\ to find the settings.json file.
The first option lets you edit the file without having to log in as admin, but might give permission problems for Transmission. You don't have that problem with the last option, but you will have to log in as admin