The electronic structures, optical and charge transport properties of various boron–nitrogen (BN) substituted hexagonal graphene nanoflakes (h-GNFs) are investigated with the aim of tailoring the intrinsic properties of pristine h-GNFs, using first-principles density functional theory. We consider coronene as the smallest h-GNF and compare the structure-property responses with its iso-electronic BN analogues. Three BN analogues of pristine coronene, namely mid-BN–coronene (middle hexagonal ring CC bonds are substituted by BN), peri-BN–coronene (all peripheral CC bonds are substituted by BN) and full-BN-coronene (all CC bonds are replaced by BN) are considered. The results show tunable opto-electronic properties depending on the BN concentrations and its position. The study also considers examining the effects of the BN concentration on the opto-electronic properties of larger sized h-GNFs. In addition, we find that the bulk electronic and charge transport (carriers mobilities) properties of different BN analogues of coronene strongly depend on the nature of BN substitution, with increasing electron mobility found with an increase in BN concentration. We provide microscopic understanding for the tunable properties by analyzing certain intrinsic quantities, such as the extent of orbital delocalization, electronic gap, electrostatic potential, reorganization energy, charge transfer integrals, density of states, etc. The study suggests that optoelectronic and charge transport properties can be tailored through appropriate tuning of the BN contents in h-GNFs, thereby paving the way for designing advanced optoelectronic devices.