Niagara gives you the full flexibility of being able to create your own custom modules. You can use the Niagara Script Editor to define your own logic flow, save your modules, and then apply them in a Niagara stack.
Niagara Script Editor Reference
To understand how to use the Script Editor, refer to the Niagara Script Editor Reference page.
Versioning Modules in Niagara
When you are iterating on creating new versions of modules, it's a good idea to work with versioning enabled so that you don't end up breaking any scenes that are using an outdated version of your modules. This page can teach you more.
We will continue to add more documentation about creating custom modules in Niagara soon. In the meantime, check out the Content Samples as a good place to pick apart existing modules and understand the logic of how they are built.