There are two commands that can be used to change the orientation of a node. The Rotate command (in menu Edit) has a submenu that allows the currently highlighted objects to rotate in any of three Manhattan directions or by an arbitrary amount.

The Mirror command (in menu Edit) has a submenu that allows you to flip the currently highlighted objects about their vertical centerline (left/right mirroring) or their horizontal centerline (up/down mirroring).

Be aware that mirroring is not the same as rotating, even though both may produce the same visual results. Mirroring causes the node to be flipped about its horizontal or vertical centerline, and thus appear backwards.