How do I use DeepL for translations in BookyAI?

Get an API key from deepl.com/pro-api — the free plan gives 500,000 characters a month, roughly one full-length book — and paste it in Settings under "DeepL API key". Then, in the Editions card, an engine selector appears next to the language: choose DeepL for an edition and it will be translated by DeepL instead of your AI provider, with your characters' names pinned through an automatic glossary. You can also make DeepL the default engine in Settings. Note that DeepL supports about 33 languages; for a language DeepL doesn't offer, BookyAI translates with your AI provider instead, automatically.