Originally, I had a library of 14,000 "items" (i.e. files and folders) and learned that the moment a library hits >5,000 items, speed is significantly compromised. It was taking 2 minutes to create a new folder in Windows Explorer view.
So I migrated the items to 4 separate libraries - all now under 5,000 items but have seen NO relief in my speed issue. Please provide any thoughts or insights you might have.