Hey @kng_ito,
I am not sure that the developer forum is the best place for this, as this strikes my more as a Node Editor end user question, but we'll give it a spin (otherwise use our Support Center).
So, you basically want to create something like this for materials, right?
6a7a22a0-3968-44a8-bc2b-ab52d1a964bb-image.png
Where the Segment.X input port on the root node of the graph is exposed in the Attribute Manager? I.e., this here:
f6c61ef4-b374-4f4c-8163-834a97f9439a-image.png
But the Color port in this case does not show up in the AM? I do not think there is a way, at least from a technical perspective, the generic "Standard Material" overrides the whole UI of that material and puts there the end node of the material graph. E.g., as shown below for the Standard Render (and this is then also called 'Inputs').
5b61aaf9-9f6f-43c2-a8a3-f3c6fc617d00-image.png
It is only Redshift which overrides this behaviour, and only when you have a RS Standard (or Standard Material) node in the graph, then it will display that. If you do not, it will default to the general material nodes behaviour of displaying the end node.
9cb2c844-172f-4cde-843c-f695da02828a-image.png
So, I would say this is not possible, and the place to go would be end user support.
Cheers,
Ferdinand