I am a newbie.
I have found a great SU tutorial at http://www.martinrinehart.com which starts with simple edges and goes right through to complex rubies.

I've been looking a something similar.
I don't think it is possible, but did you know it is possible to have a section associated with a group rather than the whole model?
Just edit the group and set up a cut plane.
Exit the group and the cut plane stays in place.
Create a new cut plane outside the group and you get the effect I think you are looking for.