I have two .blend files, and I want to get nodes from one into the other .blend file.
2 Answers
You could give a cube the material with a node setup, then open both blend files and copy/paste (CtrlC / CtrlV) the cube between documents.
Open the blendfile that you are working in then append (SHIFT+F1), then select the file you want the node settings from and go to the map Nodetree. Then select the nodegroups you want to use (so make sure you grouped the nodes in the other file). Then go back to the compositor, SHIFT+A > Group > Group you appended.