In the Rhino C++ SDK documentation for CRhinoLayer, under MemberFunction Documentation for IsVisibleInRhinoUserInderface (see copy below), I believe the (in bold below) should be that.
bool CRhinoLayer::IsVisibleInRhinoUserInterface ( ) const
Returns: True if the layer is visible in the layer manager dialog and other Rhino user interfaces the display layers. Otherwise the layer is filtered.
Here is a link to the page that contains this information:
In the future, what category and to whom should I direct these suggestions for Rhino Documentation enhancements?