In this example edge filter is used to show the edges only without body.

SOLIDWORKS - Weldment Sketch From Solid Model - YouTube 

Time 1.42-2.25

I do not why edge filter is used because I am able to show the edges only without using edge filter.

-"Select All" command will highlight all edges.

-3D sketch & Convert Entities will select all the edges.

-Delete body or Hide body will show the edges only.