The tool I used was Twine which can be found at the link below. This tool is open-source and you can use it to create non-linear stories (may have ramifications) in an external tool like the one in the image above.
There is a plugin for Unity to integrate it into your games!
This application also supports variables which allows you to decide the flow of the story and integrate quests as well.
In the future I can make a tutorial on Youtube showing how to implement in Unity!
That is all.
Hope you success in your creations!
Cheers!
Twine site:
https://twinery.org/
Plugin para Unity:
https://github.com/daterre/Cradle
If you are creating an adventure or rpg game consider prototyping it using this pack HERE