I'm changing my first approach to LibreOffice Writer with the Writer2ePub extension. I'm currently doing extensive preparation and notes for a weekly Sunday school class. I work on a 2 monitor Linux workstation. This workflow fits into what I'm already doing.
Research with
books in Calibre
Web browser
Local files
Write notes with LibreOffice Writer while researching and studying.
Output notes to epub with Writer2ePub.