Use this method to add controls to a list of controls that the WindowSplitter will internally manage. That is once you have told the WindowSplitter about controls that should be affected by the splitter movement then the WindowSplitter will take care of resizing and moving them when the WindowSplitter moves. (This method is intended for TabPanels and PagePanels, use the AddControl method for other controls).
Using this method can in most cases eliminate the need to do size calculations in the SplitterMoved event.
This method exists because there there is a bug in REALbasic which lets REALbasic brute force destruct TabPanels and PagePanels controls when the window closes no mater what the reference counter says.
The difference between AddControl and AddUnmangedControl is that, AddUnmanagedControl will not attempt to manage reference counting for then AddUnmanagedControl.