Electric-field control of the degenerate shell in a triangular graphene quantum dot

•For the TGQD with up to elecrons filled in the degenerate shell, we have calculated the eigenstates and the chemical potentials as functions of the electric field.•Based on analyzing the chemical potentials, we present the control scheme of both the shell filling and the total spin by the electric field. The single-electron can also be switched by the electric field.•The results support the possibility to use the system as a spin memory device or an electron-transport switch.