Each diagram contains a good number of shapes, thus each shape has connectors connecting to other shapes. Sometimes it is difficult to find out the relationships between the shapes.
Starting from version 13.2 (To be released in August 2016), when you select the shape, all related connectors will be highlighted automatically. Of course, you can turn the highlight on and / or off from the top toolbar.
Sneak peak at how Automatic highlight related connectors work.