I have a working C++ plugin with several commands.
Now I want my plugin to react when an object is added, edited or deleted. I found the sample for https://developer.rhino3d.com/guides/cpp/custom-undo-events/, but having trouble translating that to how to correctly implement add/edit/delete handlers in my code. (From what I have read so far, it appears that an edit = delete+add, so a separate edit handler may not be needed.)
To handle Rhino events, you will want to inherit a class from CRhinoEventWatcher and override the virtual functions related to the events you are interested in.
There is sample worth reviewing in the developer samples repository on GitHub.