Setting this attribute will move the cursor on the specified tree node,
if it is visible. If the node is in an opened tree the listview is
scrolling into the visible area. Passing the special value Off will
vanish the cursor.
If this attribute is read it returns the id of the active tree node. The
result is Off if there is no active entry.
You can create a notification on Listtree.Active. The
TriggerValue is the active tree node.