Where to begin with modifying existing Maya windows

Noob question: Where do I begin with modifying an existing maya UI window? I’m specifically trying to do some minor modifications to the connection editor. While I’ve found plenty of resources on creating UI windows from scratch, I can’t seem to find much on working with existing windows. As far as I know the windows are built around MEL, but I’m wondering if it will be possible to edit a window using PyMEL? Is there a way I can load specific elements from the connection editor into a new pyside based window?

Thanks in advance for any advice. :nod: