Now throughout the Lightroom ecosystem, as a replacement for the Split Toning panel, the Color Grading panel allows one to apply a color tint separately to highlights, shadows and midtones, controlling hue, saturation and luminance, and/or a tint globally using industry standard color controls.
Hue and saturation are controlled with color wheels (or sliders), and luminance is controlled with the slider below the color wheel.
Lightroom Mobile Access:
Replicating Split Toning
To replicate the old split toning capability, use the Shadows and Highlights tints, and set Blending to 100.
There are three new presets in the Creative section of the Presets panel that use color grading: Cool Matte, Cool Shadows and Warm Highlights, and Warm and Moody. Other presets that used to use split toning now use color grading (with Blending=100).