These are managed by calibre along with the book files, but cannot be used for conversion/viewing. Right click the Add books button to add arbitrary files as 'data files' to a book record. Allow storing extra data files with a book.Ensure metadata.opf is always written when deleting book even if it is not sequenced for backup.Fix a regression in the previous release that broke some operations in the Manage tags/authors/etc.Fix the data files associated with a book not being handled when using the Merge books and Copy to library functions.Fix a regression in the previous release that could result in empty author folders remaining in the library when the author of a book is changed.Metadata editor: Use a dedicated editor with preview for custom columns that store Markdown formatted text.Trash bin: Add a button to clear the bin.Allow displaying the id, formats and path builtin columns via Preferences->Add your own columns.Comments editor: Add buttons to create links to data files and also to folders easily when inserting a link.Edit book: Compress images: Support compression of images in the WEBP format as well.Template language: Add various functions to query the extra files associated with a book.Book details: Show a link to open the data files folder when data files are present.

Also further reduce file sizes when subsetting

Font subsetting: Add support for WOFF format fonts and CID keyed fonts.

Calibre not recognizing kindle