Change temperature for different part of the curve

I just thought of a hack to accomplish this. In Classic, add a local adjustment either a gradient or a brush. With the gradient position it so that it affects the entire image or if you use the brush, just brush the entire image. Now dial in that the local adjustment modifies your white balance how you want it. Enable the luminance Range Mask at the bottom of the selective edit section. Drag the range sliders to the part of the curve that you want to modify. Check with the "Show Luminance Mask" checkbox whether you are affecting the parts of the image you want to affect.

You can do this using the split toning control. This is found (I am assuming you are really running the cloud-based Lightroom CC and not the desktop based Lightroom Classic) in the effects section of the slider tools by pressing on the icon next to effects that looks like a black and a white rectangle on top of each other.