I am editing a leaf in shader editor, Nodes are not visible not even a material editor. How to create the nodes, or make them appear?
Without any screenshot is difficult to tell what's going on. Here some tips:
You don't have the shader panel visible:
You can split any area and choose what kind of editor show. You can create a new Workspace based on templates (click on the + next to the top tabs and choose GENERAL > SHADER).
You don't have any nodes
Select you mesh and click on "New" from the shader view. It's also possible that there are some nodes but are not in the actual view. So move the mouse on the shader editor, select all with A, and press . to center the view on nodes (otherwise you can zoom out till you see something)
Here a video showing how to split an area: https://i.imgur.com/I9lYQYM.mp4