Connection Points
To change a shape's connection points first select the shape, and then click on Connection Points under the Design tab's Shape Properties group.
You can move connection points by clicking on them and dragging them with the mouse or using the arrow keys. You can also add connection points by holding down the Ctrl key and clicking.
If you want to permanently change the connection points for a library symbol, you can right-click on it in the gallery preview window and use the Edit Symbol dialog to change all future instances of that symbol.