TreeView.SelectionSeparator Property
Decides if selected nodes should have separator between them or not.
SelectionSeparator as Integer {Read and Write}
Remarks
This property does nothing if the control is not in HighlightFullRow mode.
Possible values are:
0 - Disabled
1 - Mac
2 - Windows
3 - Mac and Windows
4 - Linux
5 - Mac and Linux
6 - Windows and Linux
7 - Mac, Windows and Linux
Without a selection separator:

With a selection separator:
See Also
TreeView Control