How to set boundary and fill with different transparency

I have a shape and I would like to have the boundary "thick" and the fill it with different colour and apply only to the fill a transparency.

Steps to Accomplish

Create a shape not filled in a wireframe displaystyle for example, with the thickness you need.
Open View Attributes>Display Styles and create a copy of yours display styles for example "copy of wireframe".
Change the Render Mode, Overrides, Edge Settings as showed in the video below.
Assign this new Dispaly style to the shape, for example opening the Element Information and choose it from the drop down menu in the Dispaly Style field.