In Textedit, is there a way to save all open files at once?
Apple offers various ways to control documents in apps in System Preferences &gt; General.
Ask to keep changes when closing documents
If you turn this off, then MacOS will automatically save documents when their windows are closed.
With this setting off, you only need to save when you create the document. After that, changes will be automatically saved as you make them, with versions showing each change. You can Close All (Option Command W), or just Quit the app at any time, and all files will be automatically saved with the latest version.
Close windows when quitting an app
If you turn this off, then Untitled documents that are open will be secretly saved (in the bowels of the user Library) and will open again when the app is relaunched.
If you turn this on, then you should be prompted to save each Untitled window in turn before Quit.