On modern GPUs performance is most often limited by power consumption limit rather than temperatures or frequency limits. However, nvidia-settings GUI app does not offer a way to increase the power cap. At least, not with RTX 2080 Ti and 440.64 driver and CoolBits 28. This is a feature request to add such capability.
I’ll note that setting the power cap is possible through the nvidia-smi CLI, so technically this should be possible.