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Joplin keeps the highlights and notes of each book as one note in Joplin, in a notebook you name, so they reach your other devices at Joplin's next sync.
Set it up under Tools, as Joplin: where Joplin synchronises to (Joplin Cloud, Joplin Server or WebDAV, such as Nextcloud), your account and the Notebook. Then use Export as Markdown at the end of a book's bookmarks and highlights; the note is sent at once and updated by the next export.
Notes that cannot be sent wait and go later, or with Send to Joplin. With Joplin's end-to-end encryption on, nothing is sent. The plugin is off at first: add it with More plugins, or switch it on under Plugins if it is listed there.