To set a link URL or controller action in a tree child node:

1. JavaScript Framework: Use frameworks like jQuery or Vue.js to dynamically assign URLs to nodes.

2. HTML Structure: For static trees, use <a> tags within child nodes:

   <li><a href="/controller/action">Child Node</a></li>
   

3. Dynamic Rendering: In backend frameworks (e.g., ASP.NET, Django), generate tree nodes with URLs/actions during rendering.

4. Event Listeners: Attach click events programmatically to nodes to redirect to the desired URL.