"Can you add the content of an arbitrary list of folders to your Shortcut?"

No, but I can add shortcuts to arbitrary folders to a Desktop folder or to Favorites.

I don't leave info scatter all over the file system. Info related to a project is in one place. If I'm the only one working on it, it's in My Documents (remapped to a network folder); if there are multiple people working on it, it's in a network share. I'll take you word that scattered info happens, but if it is scattered, how do you find it to add the folder to a Library in the first place?