move rgb curve to single r, g and b channel in curves tool

[EsTaF]

Hi all.
For example, in Lr I can copy curves settings from various channel to other.

In Ps I coluldn't found that feature.

[c.pfaffenbichler]

As far as I know that’s because it does not exist. 

But a Script could evaluate a Curves Layer and transfer settings from one Channel to other Channels. 

What is the actual problem/scenario?