When designing an app a method I have always used to present flows movements and animations within the app itself is with video prototypes. These are easy to mockup yourself using Photoshop and FCP (video editing software).
We are starting to see these methods being used a lot more. Including some of the larger design-led companies like Airbnb. The videos can be quick and to the point showing how certain navigation or elements will look and animate.
It is good to see these larger corporations become more transparent and release video prototypes allowing us to see what decisions go into designing their components, patterns, and rules.