Class CrossSectioner

const viewer = document.querySelector("vertex-viewer");
const scene = await viewer.scene();
const crossSectioner = scene.crossSectioning();

await scene.crossSectioning().update({
  sectionPlanes: [
    {
      normal: {
        x: 1,
        y: 0,
        z: 0,
      },
      offset: 0,
    },
  ],
  highlightColor: Color.fromHexString("#ff0000"),
  lineWidth: 0.5,
});

SectionPlane for more information on the section planes.

CrossSectioning for more information on the highlight color and line width.