Question error message "could not find subgraph asset with guid"

Using 2019.4 and Shader Graph 7.3.1. I created a shader graph and sub graphs in one project, then tried to copy them to a brand new URP project. The sub graph nodes in the shader graph give me this error message, "could not find subgraph asset with guid." I'm just trying to set up a demo scene for my shader graph. There doesn't seem to be any solution to this online. Has anyone encountered this?

 

Ok, it seems as though you have to copy the root folder or folders of the graphs, otherwise it won't copy the metadata I think. Initially I was just copying the graphs by themselves, which doesn't seem to copy the metadata. It's weird though, the project I created the graphs in doesn't have metadata files for them, but the new project I'm copying to does. Why is that?