@Stephane-Redon, it's done :) Thanks. Here's what I did:
SEFleXibleVisualModel* model = new SEFleXibleVisualModel(vp_file, "vp"); // my visual model
model->setName("VP_Arrows");
SAMSON::beginHolding("Display vp by arrows");
SAMSON::hold(model);
model->create();
SAMSON::getActiveLayer()->addChild(model);
// stop holding changes to the document
SAMSON::endHolding();