Thank you for writing.
does not support adding vertical track lines. This is a very specific scenario and you are the first customer asking for this feature. The only way to realize it is to inherit from RadTreeView
and implement your custom logic that covers your needs.
For example, I have prepared a small application, that only demonstrates how you can add a vertical line in RadTreeView
control. You should further develop this idea to fit your needs exactly.
Please find the example attached to this message.
If you have other questions, do not hesitate to contact me again.
the Telerik team