"Pager" button (chevron)
BCGControlBar Pro (MFC)
BCGSuite (MFC)
BCGControlBar for .NET
Putting the "Pager" button on a toolbar allows you to see hidden commands when the toolbar is stretched. This button also allows to show/hide toolbar buttons using the quick customization menu.
Toolbar quick customization menu:
Sample code:
m_wndToolBar.EnableCustomizeButton(
TRUE, ID_VIEW_CUSTOMIZE, _T("Customize..."));