Hi Stanislav,
I discussed this with our developers and they approved your request. You can track its progress and vote for it here:
Public URL.
In the meantime, as a workaround, you can try to determine whether the node is expandable or not by verifying whether the arrow next to the node exists or not. Here's an example:
As you can see in
this video, I'm using the code above to click on all items that are not expandable.
All the best,
Plamen
the Telerik team