Folks
Version 3.3.1
The close icon on the window used to show a dot when a file had been edited. It is no longer there in this version.
Instead the word edited appears below the file name in the tool bar.
Why not have both? The black dot in the red signal [red, yellow, green] was a standard MacOS signifier.
This behavior depends on whether the autosave feature is activated. With autosave disabled, the dot appears when you make an edit and disappears when you save the document. You can configure this in the User settings. See the Handbook entry for Use Versions for details:
However, disabling autosave also means that Glyphs no longer records a history of your file versions. So, be sure to regularly backup your Mac or use some other file version software like Git to keep track of your file in case you want to go back to an older version.