So, it’s very nice that the old name got updated to something that anyone can understand, but I have to ask:
Once you change OnSurface to be On, Rhino still asks you about a curve or edge to match. Why is that?
This forces the user to make an additional click for each match, which is very inefficient.
can you clarify this a bit? I’m not following you… screen shots helps a lot…
Can’t post a screenshot of a sequence of actions. How about this:
That bold line is something that I think easily could be eliminated, unless there’s a very good usability reason why that extra right-click is there (I won’t buy a technical reason). 
You can also press Enter to skip selecting a target curve and only select a target surface.
That’s still an extra operation. They add up. RSI is a real thing, and Rhino has literally dozens of “extra” manual operations.
I’m just pointing them out, especially in this case since this particular feature seems to be under active development.
Hello - How would you like to specify a curve to match to?
-Pascal
When it’s relevant. Ie, then OnSurface=Off… that’s my whole point, once OnSurface is turned on I don’t have a curve to match to do I? The tool should automatically recognize this and switch to surface picking instead.
OnSurface=On is only needed for an extra curve.
OnSurface =Off works without too extra clicking.
That’s right, there’s no extra action.
The default tool is to choose a surface, you don’t need an extra click.
I just tried this, and that is false in the WIP (and V6) I have. You can’t skip step 4 in my instructions above.
Again, nobody has explained to me why I would ever want to or need to select a curve or edge once OnSurface=On.
I checked rhino 7 WIP 7 and Rhino 6. Everything works as I’ve described before.
On 7 WIP filmed the plot of how it works.
If you need a story on Rhino 6, too, I can shoot a story, it works absolutely like 7 WIP.
Maybe you don’t. But you can.
Try… for example (I know you like a good Gif):
-Pascal
Ok, thanks! So that’s the explanation.
I’ve never done this (obviously). Is it a common workflow in Rhino?
I ask, because the most common workflow should be the default setting, and the less used should be the one requiring an extra click. Although with that workflow existing, I guess you couldn’t do a Yes/No option like there is now, but rather a Curve/Surface/Combo… which is what it really is.
EDIT: Btw, your first video… it looks dangerously like the curve is projected and not pulled onto the surface… I really hope that’s not the case?
This is indeed a very useful option.
Here’s a story from Rhino 6, the most common default workflow.
The first click of the LMB is the first edge.
The second click of the LMB is the second edge.
You can tell where the extra click of the LMB or RMB?
“the edge to be changed is pulled to the target surface”
Without a curve on the surface to match to, how can one specify the direction - x, y, z or normal?