This may be indeed a nice feature across most categories that use the series field (the Postcard category uses this field differently, so I don't see a use there). I do see a potential problem due to the manual assignment (which otherwise is a good idea, because different collectors will have different opinions about when a series is complete): There are series (in banknotes and elsewhere) where the issuing of items in the series has not yet ended. So what happens if a new item is added to the series (this could even happen to already completed series if a new variant is discovered)? Ideally (from my perspective) the series will change from "complete" to "new items added" or something like it, and I'm either notified each time this happens, or I have a list of such series with new items that I can pull from my profile (ideally from the "My Lists" dropdown), so I can go through these series, ideally get the new item(s) highlighted and can then decide if I set the series back to complete or change it to not complete. If that's not possible (or too much work), an alternative is that any series I marked as complete that gets a new item added is reverted to incomplete, in this case a notification to me is mandatory or I will never find such series. If a series will not change away from complete if a new item is added, this feature is not helpful for me.
I have not yet voted, because my vote depends on how the feature would behave if a new item is added to a series that I marked as complete. If I can either easily find such series and the new items or am notified of each new item in my completed series, I will vote yes, otherwise no.
Best regards,
Martin Stricker
I collect Starbucks mugs, christmas market mugs, gift cards, beer coasters, bottle caps, tickets, souvenir tokens, postcards, advertisement pens, bookmarks, match boxes, dessert lids + more