I have a Thinkpad T470p with a GeForce 940MX and I had the same scaling problem. I got my 150% and 175% scaling to work by changing the "PowerMizer Setting preferred mode" to "Auto" and "Select the GPU you would like to use" to "NVIDIA On-Demand". I changed then both at the same time so I am not sure if they both need to be changed or if just one did the trick. But my scaling is working now so I am happy.
I have a Thinkpad T470p with a GeForce 940MX and I had the same scaling problem. I got my 150% and 175% scaling to work by changing the "PowerMizer Setting preferred mode" to "Auto" and "Select the GPU you would like to use" to "NVIDIA On-Demand". I changed then both at the same time so I am not sure if they both need to be changed or if just one did the trick. But my scaling is working now so I am happy.