Tools for story outlining or mapping
Some sort of story outline / story map like the ones you can find in storylinecreator.com
Karan Asthana commented
Try Writemapper.I wish team write! should come up with something of their for better workflow.
Ps. Writemapper is minimal and similar in terms of the aesthetics of Write!
However there are Plenty of other mind mapping softwares are available Xmind Zen is also a good option.