BCGControlBar Pro for MFC
void CBCGPEditCtrl::ToggleOutlining ( )

Toggles outlining inside selection.

Used to toggle expansion of all collapsible nodes inside selection. If there are no collapsible nodes inside selection or if there is no selection, then toggle expansion of innermost collapsible node at the current cursor position.

If some regions are expanded and some hidden, then the hidden regions are expanded.