Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Twine - Twine is an open-source tool for telling interactive, nonlinear stories.
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
RenPy - Ren'Py is a free and cross-platform visual novel engine that helps you use words, pictures, and...
Slack - A messaging app for teams who see through the Earth!
Quest - Quest lets you create sophisticated text-based games, without having to program.