You can modify the closed path, by moving, adding or deleting nodes.

To move a node, click it with the polygon tool and then drag it on the new position, as shown below. Please note that the four-arrow symbol is appended on the pointer, to inform you that you are in the dragging mode.

To add a node, click on the path between existing nodes. To delete the selected node, press Delete.

Note: if all nodes of the path are selected, first click anywhere between existing nodes, to activate path editing.