We determine how to optimally reset a superconducting qubit which interacts with a thermal
environment in such a way that the coupling strength is tunable. Describing the system in
terms of a time-local master equation with time-dependent decay rates and using quantum
optimal control theory, we identify temporal shapes of tunable level splittings which
maximize the efficiency of the reset protocol in terms of duration and error. Time-dependent
level splittings imply a modification of the system-environment coupling, varying the decay
rates as well as the Lindblad operators. Our approach thus demonstrates efficient reservoir
engineering employing quantum optimal control. We find the optimized reset strategy to
consist in maximizing the decay rate from one state and driving non-adiabatic population
transfer into this strongly decaying state.