I have a document library that has multiple levels of nested folders. I can browse the folder levels using the Site Hierarchy component, but it requires clicking on each "plus" icon to expand each level. Is there a way of enabling an "expand all" option in the Site Hierarchy?
You can create or modify a view in your document library to show documents without the folders by expanding the "Folders" section and changing the "Folders or Flat" option to be "Show all items without folders".
Are you browsing using the Manage Site Content and Structure, not using the standard views of the Document Library?