Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
Sketch - Professional digital design for Mac.
Final Draft - Use your creative energy to focus on the content; let Final Draft take care of the style.
Affinity Designer - Professional creative software, exclusively for Mac.
yWriter - Free writing software designed by the author of the Hal Spacejock and Hal Junior series. yWriter6 helps you write a book by organising chapters, scenes, characters and locations in an easy-to-use interface.