Convert To Line & Convert To Curve 

Command:

    Menu【Node > Convert to line】        Node Editing Bar 

MenuNode > Convert to curve         Node Editing Bar   

 Convert to line

Steps：

1.Select a node.

2. Click Menu【Node > Convert to line】.

3.The curve between the selected node and the node right after converts to a line.

Convert to curve

Steps：

1.Select a node.

2.ClickMenu【Node > Convert to curve】. 

3.The line between the selected node and the node right after converts to a curve.