This is a twofer tip. You may not have known that every document window in macOS has long had a proxy icon in the title bar, next to the filename. The proxy icon is not just cosmetic. You can drag it to Mail to attach the document to a message, to a Web browser to upload it, or to any other location you can drag a document’s icon in the Finder (top screenshot, below, showing Preview in Catalina). Alas, in macOS 11 Big Sur, in at least the Finder and Preview, Apple chose to hide the proxy icon and the drop-down menu that lets you rename, tag, or move files using controls on the title bar (middle screenshot, below). Plus, the new title bar design tends to truncate file names. Fortunately, mousing over the filename expands the name and reveals both the proxy icon and the drop-down menu (bottom screenshot, below). Apple’s desire for minimalism can be confusing and I don’t always agree with their choices, but all the functionality is still present.