How to modify Outliner?

I’d love to be able to modify the Outliner panel to add a new column controlling an attribute like the mock up below, but I was unable to find where the outliner tree is created in the code. It seems to not be done in Python.

https://i.stack.imgur.com/82oCU.jpg

I wrote a ridiculously simple addon to toggle the Camera Ray visibility of multiple elements, something I’m constantly doing in my workflow. I need something more complex than the current panel I have (Quick Camera Ray), something that would let me know in a glance which meshes are camera visible or not, just like the outliner icons do with viewport/render visibility. Any tips?