I found a way around that, and thought to share it. I created the beam (Lintel) as a wall and used the cut geometry to subtract it from the host wall (for some reason it did not let me to do that with the beam created as a beam not a wall), for the wall that I use as a lintel I assigned concrete as the material so it shows now perfectly. The advantage of using a lintel instead of a detail line is that it shows up wherever you pass a section and in 3D isometric sections as well, and of course you can schedule it as well
Karzan