Wondering if this would be a desired enhancement among the surfacing community.
If we can extend a surface in a single command, how about retracting a surface in a single command versus trimming by various means.
The quickest way I have found to "retract" a surface, ie trim, is to create a face curve on the surface and trim using that curve. However, I can't tie that to a parameter, that I know of.
Another is to create a ruled surface and then offset it.
Others are planes, other created surfaces, etc., but for a plain old edge type of offset, it would be nice to be able to have something like extend....but retract.