There are a few easy steps that should be carried out to add support for new SVG elements:
Add an entry that describes the SVG element in the ElementType enumeration in SugTypes.h.
Create a new class that will represent the SVG element. This will most likely inherit from the SugElement class. The constructor of this new class should call setElementType(SugTypes::ElementType), where the parameter is the new element type you created in the previous step.
Create specialized accessor functions that will retreive information from the SugElement::mAttributes variable, if needed.
In the parseElements() function in ParseSvgToObject.C, add code that will create an instance of your new class when the appropriate node is found by the parser. You can also do any special purpose parsing at this point as well.
Take a look at any of the already-defined classes for a working example of these steps in action. Upon completion of these simple steps, any renderer you use should be able to utilize the new class you created to render the SVG document.