Add/Remove shelves to multiple books without changing the other shelves #543
Description
Right, now when selecting multiple books in a collection and editing the selection, it seems it’s only possible to overwrite shelves on all the selected books: select which shelves all these books will be in or out, and all the books will be the same once saved.
However, it seems useful to me to be able to add shelves to all the books, or remove shelves from all the books, without loosing all the particular other shelves each book might have had on their own.
The current behaviour is actually slightly unexpected and saving can become a destructive action resulting in the loss of a personal classification on hundreds of items (didn’t happen to me hopefully, but almost! hence why I’m opening this)
Example of use: having shelves for specific types of books (“comics”, “books about games”) and shelves for book locations (“copenhagen”, “villeurbanne”). It would be useful to be able to change the shelves for location without loosing the individual shelves for type.
I could be done by implementing a three-states checkmark UI element ([ ] not checked, [?] different values, [x] all checked), or by changing the UI (for example separate Add items to shelves / Remove items from shelves sections in the Edit selection dialogue. It would also be welcome to add counters to tell you how many selected books are currently in each shelf.