This window allows you to change the type of an operator. To access this window, click 
on a node.
Operator
Select an operator type from the drop down menu.
Keep Name
If this option is turned on, the new node will have the same name as the old node. Otherwise, the new node will have the default name for that type.
Keep Parameters
If this option is turned on, the parameter values of the old node will be applied to the new node. This only works if the new node has some or all of the same parameters as the old node, for example, changing a Null object to a Geometry object. Otherwise, the new node will have the default name for that type of node.
Keep Network Contents
If the old node and the new node are both subnet types, turning on this option causes the new node to have the same contents as the old node. If turned off, any contents of the old node will be discarded.
This option is only useful if both the old and new nodes can contain other nodes.