Cloning UE4 codebase (https://www.unrealengine.com/en-US/ue4-on-github) is very useful even if you don’t plan to build the latest engine version. Here are a few use cases that I use regularly myself!
Finding C++ code behind a blueprint node
You know how to do things in a blueprint but don’t know how to go about it in C++? Why not look at the source?
Hover over a node for a tooltip to be displayed. Note the text “Target is Audio Mixer Blueprint Library”. The target name is the name of the class and conveniently name of the file we are looking for!
For navigating inside the engine code, I prefer using Visual studio code (https://code.visualstudio.com/). Simply go ahead and open the whole “source” folder from “UnrealEngine\Engine”.
After hitting “Ctrl+P” and writing “AudioMixerBlueprintLibrary” (without the spaces introduced in UE4 Editor tooltip), we are given to files:
Go ahead for the implementation file and use good old “Ctrl+F” to find the function by blueprint node name: “GetPhaseForFrequencies”!
Searching for the usage of class across a whole codebase
You found a class in Unreal Engine 4 documentation and now you are unsure about correct usage? UE4 codebase is so large that the chance is, that the class has been used somewhere in the engine.
In the VSCode, go ahead and search the whole folder using shortcut Ctrl+Shift+F.
For example, for a TCircularBuffer we can find at least a test file at “Runtime\Core\Private\Tests\Misc\CircularBufferTest.cpp” which shows exactly how the class should be used.