A librarian villager trade rebalance, allowing you to 'teach' librarians enchantments using books.
Bibliothecary
Bibliothecary is a Paper plugin that attempts to rebalance the librarian villager enchantment system, pushing players to go exploring to find enchanted books, but allowing the books to be farmed after obtaining a copy.
The plugin stops villagers from trading random books, and instead allows you to 'teach' them, requiring you to obtain a copy of the enchanted book from exploring structures or through things like fishing, then allowing you to copy it using villagers.
How to use
To teach a villager to trade an enchanted book, you first place it on a lectern, then when a villager using that lectern as a work station is about to gain an enchanted book trade, it will use the book on the lectern and begin to sell that book.
If there is no book on the lectern, the villager will skip the enchanted book trade.
Configuration
By default, villagers cannot learn to sell enchanted books with multiple enchantments or enchanted books with enchantments like Soul Speed, but these settings can be changed in the config.yml
If you have any suggestions for new configurable features, join the Starshooter discord server and request them in the suggestions channel.