Please consider adding a "Link" search criteria so it's possible to create Smart Collections entries that use it.
After seeing
Nora's helpful hint, I'm now aware of
Any Link Name|Type|URL search criteria. A simple
Any Link Name is not <empty> Smart Collection matches Library entries with links, resolving that issue.
Speaking of links, here's something unexpected I encountered:
Running
Option-Help > Validate Links on File created an excluded "Links not Found" collection with entries from the aforementioned SC, plus a couple others from another excluded collection. Being excluded, deleting that "Links not Found" collection would have also removed entries within it, which isn't what I wanted. Workaround was to make it an included collection, then delete it. An unwanted side effect was that the couple entries with links from the other excluded collection became part of the Library collection, which I removed by running
Include Collection in Library and
Exclude Collection from Library on that other collection.
I hadn't anticipated it working that way, but it partly makes sense why it did. Just have to be careful in other usage cases where entries intended to only be in excluded collections won't unexpectedly be included in Library. It's confusing when that happens because it may seems like there are separate/multiple copies of an entry rather than it being only a single entry in the database. For example, were entries in the excluded "Links not Found" collection that
Validate Links on File created separate copies or the same instances?
I still don't know how to reliably tell when different entries that
look like clones are distinct from, or the same as, each other. Sort of a "how many copies of an entry exist in the database when it appears multiple times in one or more collections?" question. Popping up the
Show in Collection context menu sometimes helps, although for only a single entry at a time.
And I wouldn't mind a "Link" column that displays the first link for an entry (when multiple links exist).
I still don't see a column attribute (similar to URL) to display first link pathnames in List view, but maybe it's in my blind spot? Even without that just the
Any Link … criteria are a big help.