Apps similar to Govel include Zettlr, which is free and open source. Other options are Typora, ghostwriter, Manuskript and Scrivener. You're spoiled for choice with Novel Authoring Tools like Govel: we list more than 50 alternatives for Windows, Mac, Linux, the web and iPhone.
SceneWright Studio is a media-rich story planning and writing application. It takes the time proven index card method and digitizes it, adding almost every resource you could want on its own card.
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StoryGuard is a campaign notebook built for tabletop RPG Game Masters. Instead of a wiki you update by hand, you write your session notes and StoryGuard keeps track of what actually happened: who's dead, who's holding the cursed sword, and which secrets your players...
