In macOS the green button (upper left corner of each window) makes a window FULLSCREEN and not (like with other operating systems) just maximizes the window.

There is a trick to change this behavior though, so here 2 functions I made to disable and enable the fullscreen behavior.
You can disable the fullscreen behavior (becomes maximize) and enable it again if needed.

procedure DisableFullscreenButton(theForm: TForm);
var
  theWindow: NSWindow;
begin
  theWindow := NSView(theForm.Handle).window;       // Form1 is the name of the main form - adjust as necessary
  theWindow.setCollectionBehavior(theWindow.collectionBehavior or NSWindowCollectionBehaviorFullScreenAuxiliary);
end;

procedure EnableFullscreenButton(theForm: TForm);
var
  theWindow: NSWindow;
begin
  theWindow := NSView(theForm.Handle).window;       // Form1 is the name of the main form - adjust as necessary
  theWindow.setCollectionBehavior(theWindow.collectionBehavior and NSWindowCollectionBehaviorFullScreenPrimary);
end;