I am developing a pligin (as well as a model of electrical objects) that uses the lamps and other electrical model objects to calculate the wiring requirements. for this purpose I need to add some extra attributes like power consumption, generated heat, complying standard and so on. or to add the max ampere to a wall mount plug.
How is it possible to edit the current furniture items? and also how can I use other free tools to construct such model objects.
A concrete instruction would be highly appreciated.