Determining Source File to Edit

Is there documentation that helps determine what parts of spark & it’s GUI correspond to the underlying source code?

For example, I want to set the “Show offline Users” option to be “on” by default, and I want to set “group offline users” to be off by default.

I know how to edit the java source code, but short of a bunch of hunting and tracing, is there any shortcut?

Thanks in advance for the guidance.