We demonstrate a rigorous multimode engineering method to achieve multifrequency superscattering with flexible controllability in a subwavelength graphene/hexagonal boron nitride (hBN) cylindrical system. Through delicately tuning the chemical potential of graphene, different resonance channels of the proposed stucture can be spectrally overlapped to construct the multiple superscattering points. Consequently, the scattering cross section is enhanced effectively and the so-called superscattering beyond the single-channel scattering limit can be attained. Numerical calculations on scattering spectra, near-field, and far-field distributions are performed to confirm the scattering enhancement. The general principles presented here may suggest an accurate and efficient approach to actively tune the light-matter interaction at the subwavelength scale.