Who can give me a simple example of add-on what supports or uses MFC?
I wouldn't recommend using MFC for plugin development, and I doubt you will get any examples of it. A plugin is not an application, and therefore does not have the freedom to do things MFC might assume are possible. You will certainly have problems if you use it for the UI, e.g. you will not be able to integrate API controls for attributes like pens, materials, etc. Your best bet is to build your plug-in on the ArchiCAD API.
Which features of MFC do you hope to use?
Ralph Wessel BArch