BCGControlBar Pro for MFC
BOOL CBCGPMDIChildWnd::IsRegisteredWithTaskbarTabs ( )

Tells whether the MDI child is registered with Windows 7/8/10 task bar tabbed thumbnails.

This method return TRUE if MDI child is registered with Windows 7/8/10 task bar tabbed thumbnails.

This can be TRUE only under Windows 7/8/10 when MDI tabs or MDI Tabbed groups is enabled.