The name of the field in the listname working list, the value of which will determine if a tree item should be selected when displayed. This is only valid for unlevelled lists and will be ignored if listtype is "levelled".
Default value
Blank. Tree items cannot be pre-selected.
Valid values
The name of the field in the working list that will contain a value of 'True' if an item in the tree should be selected. If set to 'Freeze', the item will be selected but the associated 'on select' action (if applicable) will not be triggered.
