If I have an edge loop that I want to slide up an edge that is perpendicular to the loop, how do I pass this information on to the Transform SOP?

I hope I'm not mising the point…

If you want to transform perpendicular to an edge loop you could do this using the construction plane.
Holding down th c key will let you click on three points of your geometry to define the construction plane orientation.
Be sure to click on three which best lie in the plane of youe edge loop.
This will snap the construction plane to the points you selected.
Make sure you first disconnect the jack by pressing the ‘ key. If you don’t, you selected geometry will orient at the samre time as the jack.
On your transform jack, a right click should give you some transform jack options. You want the one that orients it to the construction plane.
Then hit ‘ again to reconnect the jack and transform your geometry.
hope that’s what you're after
Jerry

If the loop isn't planar there's no way to accurately
move it all at once, unless the loop was created with
polysplit (edit ‘override bias’). If some points move
the wrong way you can edit those with edit sop; switch
on the template flag on the previous sop and also geo
edge snap to make things easier.

Hmmm… it would be nice if I could align one axis of the transform jack to match an edge that I pick to move the edge loop along. I remember being able to do this with a different modeler. Orienting the c-plane to the edge, and then aligning the transform jack to the c-plane sounds like it would work, but seems a bit cumbersome. Is there any way to do it without messing with the c-plane?

Right-click on the transform handle and choose Start Orientation picking.

Thanks Edward

noticed someone on odforum was asking about the same feature to redistribute the spans on a model. That is what I am trying to do also. Can/will this be a future feature without having to detach/reattach the jack?

I suppose it could. However, I can't see into the future.