Plot Factory - Online story planner, organizer, and writing application.
Notepad by Braden Farmer - Notepad is an app by Braden Farmer that offers features that let you write and save plain as well as rich text notes by using HTML or Markdown.
World Anvil - World Anvil is a worldbuilding tool for Authors, Storytellers and worldbuilding lovers.
Scrittor - Scrittor app allows users to create notes so they can store all their ideas and thoughts on their mobile phones to view them later.
Scrivener - Scrivener is a content-generation tool for composing and structuring documents.
Notebook.ai - A smart notebook that grows and collaborates with you