Assume that you you have made a node tree to set up a new material for an object(Let us say an UV Sphere). Now you add another object (let us say a Cube). To copy the node tree from UVSphere to the Cube follow these simple steps:
1. Select the UVSphere. In the node editor set up a simple material node tree and save it. Now select all the nodes using Box select option. To copy these node tree to clip board click on the first floppy disk (like icon in light yellow color on the menu bar of the node editor.
2. Select the Cube,click on new material and click on new. You will see a Diffuse BSDF node connected to the Material Output node.Click inside the node editor window using LMB. Now click on the floppy disk icon on the right side. The node tree of the UVSphere will be pasted here. Select the 3D window and press Shift+Z to see the rendered view of both objects with the new material. Change in material setting of the nodes of UVSphere does not affect the material settings of the Cube.
