Updated June 8th, 2019.
Sometimes you have a document open but you don’t know where the document really lives. Maybe you used “Recent Items,” maybe you have two documents with the same name and you’re not sure which one you are looking at. Maybe you’ve made a new document, saved it, but you can’t tell where. There has to be a way to tell where an open document is saved, right?
Just ⌘-click on the title of the document, in the title bar, and you’ll get a drop-down menu showing you exactly where it is. If you slide down that menu and select something, you’ll open that folder. Handy. See below.
Some document windows will give you “something” if you click and hold– without the Command key– on the window’s title. Some document windows have a little downward-pointing arrow that gives you other options. Worth exploring, sure. But for finding where an open document’s saved, the ⌘-click always works.