You have here a particular example with a complete electrode model. The current version of Brainstorm cant handle this specific case.
A possible solution is to use the volume masks (segmentation) of you model (including the head tissues and the electrode body), then you can construct the tetrahedral/hexa mesh from the masks. You can check the iso2mesh toolbox and particularity the function "vol2mesh" .
Let us know the results, Brainstom may add this feature in the future.
No not yet. We have generated mesh using our framework and got the forward problem results and we used our volume conductor model to get forward problem results using duneuro. we compared these two results. I will share the results once finalized.