Attach notes to Folders?
 

How can I include a note with a Folder?

I have many Folders which hold Projects which I will process identically. I'm looking for a way to store notes regarding what is in the Folder and how to process those Projects.

From a broader perspective: what are all the attributes/metadata/tags that can be assigned to Folders?

As far as I understand folders can simply have a name. They are used to generally group projects in respect to each other and are not visible in Context view. In my use they represent my areas of focus. Although, I do use a subdivision by folder within my R&D area of focus. These divisions, for me, are self evident.

Without a more detailed explanation of the general structure and workflow you are implementing within OmniFocus I could not do more than suggest you consider using the default modes, Projects and Contexts, for planning and processing respectively. As folders do not show up in Contexts, if adding notes was possible, viewing notes placed there would be unavailable when processing tasks. Could project notes be a solution for you here? If so there are scripts to use template projects which would add these notes for "identically processed" projects to each implementation of the project.