Chapters: notification when already added

[lottebelice]

When I look for chapters in the 'Related chapters' dimension and add them to 'Saved enrichments', it can happen that I add the same chapter more than once. Example: when I look for chapters with the entity 'zilver', add a couple and then look for others that are related to the entity 'fries', some chapters also appear in that list. When I then add the same chapter to 'Saved enrichments', I'd like to get a notification that says 'already added', or even better, some sort of visual clue in the list of found chapters that it's already been added.