Visualization is an important part of BoofCV and its development. This is evident in examples and demonstrations both of which heavily rely on these tools. Having controls which let you modify tuning parameters in real-time is a core part of BoofCV's development process.
The documentation is a bit sparse for right now, but you can find much of it by browsing the source code inside of demonstrations and examples. If you see something that you like just open up the code. Below is a list of example code that you might find helpful
Almost all Demonstrations in BoofCV extend DemonstrationBase as it provides a structure for abstracting getting images, video streams, webcams, and files inside a GUI.