The application title can be changed from the IDE’s main menu under ProjectOptionsVersion Info. For Windows, this is “InternalName” property. For OSX and IOS, the CFBundleDisplayName property, and for Android, you will need to change the Label property (Note: you can also change the label property in the template manifest). Apparently there is a work around to make it work on the Windows platform:
procedure TForm1.FormCreate(Sender: TObject);
var
app: HWND;
begin
//Application.Title := 'New Application Title';
app := GetWindow(WindowHandleToPlatform(Self.Handle).Wnd, GW_OWNER);
SetWindowText(app, 'New Application Title');
end;
Check out the thread on the official forums about it.