How to make connector caption become transparent

In my diagram the connector lines are being covered by their caption.

Caption overlapped with connector

This actually is one of the presentation option on the connector caption which helps to avoid the text overlapped with the connector line. You can override this by right click on the blank area of the diagram and select Connectors > Paint Connector Through Label.

Turn on paint through label option on diagram

After that the caption background will become transparent.

Caption now show with transparent background

You can set this become default for the diagrams created later inside Project Options:

1. Go to Window > Project Options.
   

   Open Project Option

2. Select Diagramming > Connector and turn on Paint connector through label.
   

   Set it as default for newly created diagram inside Project Options

From now on all newly created diagrams will have this option set as default.