P: Want to change Layer Comps inside a Smart Objects

+1  The feature is  pretty  useless till we could save smart objects  comps within parent file layer comps and switch them instantly .    Now I have to do 10 copies of a smart object to represent it's different states.It turns layer stack into an utter mess

Another problem:  re-saving and updating  hi res 16/32  bit smart objects takes forever .   I love how Affinity Photo updates master file instantly once you do something in embedded doc .   Would like to see same in Photoshop.   As an option maybe.     

if the numbers of artboards make it difficult to navigate you can try using ctrl click on the artboard in the layer panel to navigate.
as for the performance issues, I suspect, you may be an osx user.
I'm sorry to say that the windows version performs just waaay better in that regard in my experience
also for the most part in my workflow all artboards in a psd share the same smartobjects (often linked) I believe displaying 10 states (via smartobject layercomps) of 10 different smart objects should have a far lesser impact on performance than displaying 100 different text object for exemple)
my intuition is that smartobject as being black boxes should perform better than other (in place editable) element 

I have tried this approach, but there are a couple problems with it in my experience. One is simple but annoying; it's difficult to navigate documents with many artboards. I know it's a small thing but it slows you down. The bigger issue I run into is performance. At my job it isn't unheard of to be doing anywhere from 7 to 20+ pages of an application or site in 2-3 screen sizes. Photoshop handles the large documents well when not all layers are on at once, but as artboards stack up it gets slower and slower. Artboards are also still a bit buggy, although they are consistently improving, which is a good sign.

This is also what I have found to be the easiest workflow at the moment. 
Artboards containing smartobject that may contain layer comps for different states.  
Other than that, I am looking forward to seeing what Adobe XD can bring to the table. 

for what it's worth, an alternate and more convenient workflow for what you describe is to rely on artboards rather than layercomps in the master psd.
page components (header, footer, etc...) as smart object are very useful, but you have to lay out pages states with artboards (thus copying the smart object) if you want to solve the current smart object limitation

I would also like to see the further implementation of saving a smart object's layer comp state in the master document's layer comps. Here's a case study I use constantly in UI work:

Create smart object for header (so I can update across pages in one place)
Create layer comps in that smart object for each active page state (to easily cycle through which nav item is active)
Create layer comps in master PSD for each page (each one needs an instance of the header object, but I'd prefer to just have one instance and for the layer comp state to be recalled)

Basically where layer comps have options to capture visibility, position and effects of layers, it would be SO useful for people who use layer comps as a workflow to also save smart object states.

indeed, to be rigorously correct this topic should not be marked as implemented. (as it is only partially implemented)
Also if anything could be done to consolidate all the disparate topics and votes into a single topic, that would be of great help, thank you.

"I would like to select which Layer Comp inside a Smart Object I want to display on the Root Document where it is placed"

This has been implemented :)

"and also store that again in a Layer Comp of the Root Document."

This has not been implemented 😞

this idea his indeed diluted into several topics:
http://feedback.photoshop.com/photosh...
http://feedback.photoshop.com/photosh...
http://feedback.photoshop.com/photosh...
etc...

this unfortunate duplication, may explains the relative low interest generated by this topic.
for anyone working with layer comps and smart object this missing feature is a real shortcoming. It's surprising that no one in the dev team figured this out earlier.
This is a more than 3 years old request...
Is there any other channel where our voice could be heard more appropriately ?