Q: I want to create a smart collection within an existing smart collection.

A: No, you cannot create smart collections within smart collections. A smart collection is an active “filter”, that is updated every time it does get a “focus”, aka you are clicking on the smart collection.

What you can do to “somewhat” get around this limitation is to create a collection set:

  1. Create a “regular” collection
  2. Create the various smart collections
  3. Create the collection set that contains all these smart collections.

You can expand the smart collections by adding them together, you can’t shrink them (meaning a subset of the smart collection), by doing various filtering within the smart collection.