Option to 'edit data flow' missing

Why is the option to 'edit data flow' missing on some of my data flow lines between components?

If you do not see the option to 'edit data flow' when right-clicking a dataflow line between two components, the most likely cause of this is the dataflow line not being anchored correctly to the components' connection points.

To ensure it is anchored correctly, you need to drag the data flow line and ensure it connects to one of the connection points shown as 'x' around the component.

Once you have ensured the dataflow line is anchored correctly, you should be given the option to 'edit data flow' when right-clicking the dataflow line.