I'm starting right now to look into plasma, my language of choice would be python, which I'm learning. I can mostly understand C++ but can't code in C++ myself.

Now on to the problem. I've a concept in my mind for a different taskbar so I opened the tasks source code... but I can't really find anything I can understand. For example how does the applet display context menus on a right click? They are obviously defined elsewhere but I can't find where they are invoked.
Apparently it doesn't even use the tasks data engine, which by the way does not supply the PID of the process behind that task (why? ).

Maybe it's a bit advanced but that's what I've got an interest in: if I spend time on plasma I'd rather do so on a project that can keep me focused.

The Tasks applet appears to be using libtaskmanager, which is one of the libraries provided by KDE Workspace. You can find its documentation at api.kde.org. I do not know if it is exported to Python or not unfortunately.

Thanks for the heads up, I'll try to find more information about the library and its python bindings.