Keeping trim line when untriming

keeping the trim line when untriming in rhino is a little frustrating,

Autodesk Alias and Maya have a slightly different solution.

They have a different geometry form, which is called CurveOnSurface (CoS)- which is a 2D Curve that exists in the Suraces UV Parameter Space… and the great thing about it is… that it sticks to the uv space!
you can untrim, and the curve stays! So its easy to retrim, or to add more trim curves to the trim operation. +the Curve is stuck to the Surface.- If you move the Surface, the CoS moves with it!
I find that behavior VERY usefull for complex Trims, (like complex Grill meshes for example)
I guess that rhino internally does the same thing, but doesent keep that trimcurve-Information when untriming!? (or simply doesnt show us?)
Is that so?
And If it is, would it be possible to access that trimCurve-information like in Alias?

When you use Untrim, to keep trim curves, set KeepTrimObjects to Yes. DetatchTrim is an internal alias that sets KeepTrimObjects to Yes automatically.

Yes, but I find the “Alias” Way of “storeing” the TrimCurve within the Surface much more comfortable…
and as written above, I believe that rhino internally uses the same concept, but not showing us!
Can Some developer clearify/explain how Rhino is handling this?