I had one user that indicated this might be possible by making the section as a simplified rep at the PART level, as opposed to doing the family table. I could not get this to work, and that user said that he has a document that he'll forward to me that explains how to do that.
But, in the meantime, I finally DID figure this out, on my own, but it took me a while. And when I got it all done, it didn't work for me anyways, because the assembly that I wanted to do this on happens to be a welded assembly, and the welds under the cross section "area" are all displayed, and there doesn't appear to be away to make them go away with hidden view modes. In order to get rid of them, I would need to put them on a layer specific to that view, and then hide them. I could do that, and get it to work for me.
But, these are the steps that I had to go thru to get this to work:
Go to the view in the drawing
Create a NEW cross section in that view
I chose OFFSET, because I wanted to control the "shape" of the cutout (NOTE: the OFFSET section REQUIRES that the end lines be straight, so your sketch will need at least two straight lines)
I chose BOTH SIDES, but I don't know that it makes a difference
Enter a name
Sketch the "cut" that you want ON the part that you want to cut
Choose refs
Create sketch (with at least end lines straight), and end sketcher
