P: Show stack in Smart collections

My issue was with the concept expressed by an image "show(ing) in the smart collection" some enduring behaviour particular to this smart collection, such as stacking or custom sort order within this.

If an image has got an attribute which says that it "is stacked" (vs not being stacked) then either that is a universal attribute (in which case, the question is: stacked with which other images and how), or else, it applies only for a given context (be that Collection, or Folder) wherein a stable set of images will repeatably appear. A context within which each image can sensibly remember its own placement.

My contention is that this same idea does not make practical sense when it comes to a dynamic-membership Smart Collection. Smart Collections come and go, can be deleted and recreated under the same name or different name, their inclusion rules change over time, the image attributes that qualify or don't qualify them for a given rule change over time.

What is each image to remember, and how, about all of these SCs? (just in case it might dynamically appear, or reappear, in any one of those SCs tomorrow),

or otherwise, what is each SC to remember, and how, against all of these images? - just in case one of them might dynamically appear, or reappear, in this SC tomorrow).

Like I said: It's the 'local' thing. If stacks were global, meaning a stack would apply anywhere and an image could therefore be in only one stack, then Lightroom could tag an image as being a member of a stack, just like it uses other tags. Consequently, it could show in a smart collection that the image is a member of a stack, even if the other members of that stack do not fit the criteria of the smart collection and aren't shown in the smart collection. That is how Apple Aperture worked.

The important distinction here is between folder OR collection membership (which are part of the persisting attributes for each image), as opposed to Smart Collection membership (which constantly refreshes itself within the Catalog as a whole, being the live result set from a database query).

As I understand it there is not (and probably cannot be) anything persistently stored concerning Smart Collection memberships within each particular image's metadata, against which any stacking or custom sorting information could be remembered.

Nor AFAICT could the Smart Collection itself sensibly remember particular sorting or stacking info, for a dynamically floating set of images.

I think you are missing the 'global/local' point. A number of images can be stacked in one location (a collection), but not in another location (another collection, or their folder). In fact, one of these images may be stacked with other images in another collection, meaning it is in two entirely different stacks. So how should Lightroom show this if you search for these images in a smart collection, and the smart collection does not specify a particular location?

The question is not about stacking images in a smart collection.  They are search results.

There is no reason why a stack can not be in a search result. s.

If Lightroom can show stacks in your library it can also show stacks as a search result. Or you should at least be able to filter them in the library.  

Stacks are local. If you stack images in one place (their folder, a collection), then they are not stacked in other places. A smart collection is a search result, that is why you cannot stack images in a smart collection and why stacking in another place is not carried over when the images show up in a smart collection. I use color labels for this too, and I label the brackets in purple. Then I added 'Label color is not purple' as criterion to all my smart collections.

For several reasons this sounds quite problematic.

A workaround may be to number rate or otherwise flag the top member for each stack. Then within the context of the Smart Collection you can filter on this. A named view filter is very rapid to recall e.g. at the right hand end of the Filmstrip. And you can make a different named view filter which cancels what the first one does.

Filtering to show only images higher than three stars say, would then be equivalent so far as what images you see, to collapsing all of the stacks. So a distinction between primary image and subsidiary images, can be represented by these other means. And removing this view filter would then look like expanding stacks again.

This method works on the attributes of each individual image taken alone - which is all that a Smart Collection, as currently designed, can ever take any notice of. Stacking, and custom sorting, AFAICT rely on an association of the images concerned, within a persisting "place".

Smart Collections work on-the-fly and in-the-moment - no persistence, no memory. There is no there there.