This study systematically investigates the supramolecular assembly of iodoselanes (organoselenenyl iodides of the general type ArFSeI, where ArF is a perfluoroaryl group) bearing different terminal perfluoroaryl substituents (C6F5, NC5F4, C7F7) to elucidate the geometric and electronic prerequisites for multifunctional σ/π-hole donor behavior. By cocrystallizing these iodoselanes with bifunctional nucleophiles (4,4′-bipyridine, PyCCPy, PyNNPy), we demonstrate that terminal substituent modification acts as a molecular switch. This modification enables a predictable transition between discrete heterotrimeric assemblies and extended polymeric networks. Specifically, the NC5F4-substituted iodoselane uniquely exhibits consistent trifunctional behavior, engaging simultaneously in halogen bonding (HaB), chalcogen bonding (ChB), and π-hole interactions, across all nucleophilic partners, including those with lower nucleophilicity and widely separated binding sites. In contrast, the C6F5 analogue displays trifunctional behavior only with specific nucleophiles, while the bulkier C7F7 derivative exclusively forms discrete heterotrimers. Crystallographic analysis reveals that the “zigzag path” packing pattern, stabilized by π-stacking and secondary Se···I interactions, is a critical geometric requirement for sustaining this trifunctional mode. Theoretical calculations (DFT, QTAIM, NCIplot) quantify these interactions, highlighting the dominant role of electrostatics in HaB and dispersion in ChB and homodimerization processes. These findings establish structure-based design principles for engineering programmable NCI networks, transforming iodoselane-based crystal engineering from an empirical to a predictive discipline.