True to allow user editing of treeview nodes. The user will then be able to
edit all nodes in the tree by executing a slow double click, i.e. slowly pressing left
mouse button two times in a row.
If you would only like to allow editing of some nodes in the tree, you need to
set this attribute to True and you need to listen to the Treeview.StartEditing
attribute. Treeview.StartEditing will then be triggered whenever the user
attempts to edit a node and your callback can return False to forbid editing of
certain items. See Treeview.StartEditing for details.
To get notified whenever the value of a treeview node changes because the user has edited it, you have to listen to the Treeview.ValueChange attribute.
To manually start editing of a treeview node, call the Treeviewnode.Edit method.
Please note that this attribute only applies to treeview nodes. If you would like
leaf labels to be editable as well, you need to set the Treeviewcolumn.Editable
attribute to True.
Note that on AmigaOS and compatibles this feature is only available on MUI 4.0 or higher.