Odd effect. Unsure if FFF or Calibre.
I have a #readinglist series column, managed by Reading List plugin. I have FFF set to add books to a reading list but also tested with a book already on the list.
The seriesUrl is also added to this. However, it doesn't appear in the Manage dialog.
I will ask in the other thread if there's a way to remove the phantom link.
EDIT:
It seems this is a Calibre issue.