This Plugin is already in use, and it showed me, in use by: config/system/shares/sharedfolder. Like the path in your picture.
But i dont understand how to delete this. Just reset all permissions wont help, and i dont find the path /config/system....
My Linux knowledge isnt good enough so far.
In the future i will use the way you told before. And dont put a new hdd in, before "reinstall" the old one.
On the other hand is fun to learn something about the whole system.