Application.ShowWindowsInTaskbar Property (Excel)
True if there’s a separate Windows taskbar button for each open workbook. The default value is True. Read/write Boolean.
When set to True, this property simulates the look of a single-document interface (SDI), which makes it easier to navigate among open workbooks. However, if you work with multiple workbooks while other applications are open, you may want to set this property to False to avoid filling your taskbar with unnecessary buttons.