I encountered the very same issue, and sunag kindly disclosed the process.
import { uniform, MeshBasicNodeMaterial } from "three/examples/jsm/nodes/Nodes.js";
const myUniform = uniform( 1 ); // you can put number, Vector*, Color and others
const nodeMaterial = new MeshBasicNodeMaterial();
nodeMaterial.colorNode = myUniform;
// changing
//myUniform.value = .5;