Trying to figure out Layer Comps

Question

I recently found out about Layer Comps, and I'm trying to use them.  Does anyone have a pointer to documentation that'll tell me what they can and CAN'T do?
Here's my situation...  Normal image, go into PS from LR and do my "normal" editing.  When I'm done I have my have dozen layers.  I do a Merge Visible, then
realize I want a Layer Comp of the image without the Merge Visible.  So, I create one with the Merge Visible layer turned off. 
Then, I go back and turn on that layer, then do a free Transform and shorten the image so it'll fit an 11x14 the way I want...  It started 4288 pixels high and I shortened it about 3-400 pixels.
Create ANOTHER Layer Comp.
Then, I look at it and decide I'd like a black & white version so I put a B&W layer on the image.  Adjust and when I'm done, create a third layer comp.....
Looking at the image I realize I'm gong to need a small version for the website, so I turn off the b&w layer, crop again to 1024x768 and create a final layer comp.....
But, once I think about it, I realize I should do my crop to 1024x768 from the image PRIOR to the shortening to fit the 11x14, so I go back and activate the first layer comp I
created, that SHOULD just have my original, basic layers...  Which is appears to, BUT the image is shortened.  It appears that my cropping or using the Free Transform
to alter the image IS NOT undone when I go back to the earlier Layer Comp...
All the stuff I've read so far just tells me how to create one, copy it, and delete it.  But I haven't found the information the enables me to use the Layer Comp to move back in time
so I can crop in multiple shapes and things like that...  Am I expecting something from the Layer Comp that it can't do, or am I doing something incorrectly?
I'll keep playing to see if I stumble on the answer, but I figured I'd ask the experts in here.

Answer 1

davepinminn wrote:
Are the snapshots in History persistent across sessions?
No...
There are useful tutorials on how to use Layers Comps out there...but the bottom line is Layer Comps store the state of visibility of a certain set of layers/groups. Ig you change the layers or groups by adding/deleting layers/groups, you'll need to update the saved layer comps you made. Try right-clicking on the layer comp to update a saved comp based on changes made to the various layers/groups that existed when you made the comp. Yes, it's a brain teaser…none of this stuff is "easy" until you leaner how they are supposed to behave (and then learn how to take advantage of the functionality provided).