the Mädler & Kuncel models only support monopolar stimulations.
We are working on a FEM-based model in Lead-DBS that would support any kind of stimulation but that is not publicly available yet. If you do urgently need such a model for your research you can contact me to think about a collaboration on this – the reason being that the new model still needs a lot of support, is buggy, etc.
I’d estimate we will release the model publicly in ~5-6 months.
Hope this helps.