Although aliases don't have children or descendants of their own, from v5.8.0, an alias in action code (such as queries) can act as a proxy reference to such descendants. Previously, is was necessary to write every(descendant(original),$Checked whereas now the same can be queried, via an alias in scope by using every(descendant(original),$Checked).
In an agent query, we may want to search for notes whose children or descendants share a property:
Query: $ChildCount>0 & every(descendant,$Checked)
This will find all notes that have a child, for which every descendant is checked.
In previous versions, it was necessary to reference the original of the alias, since the query applies to an alias, and aliases have no children. As of v5.8.0, an alias' children are, for the purposes of actions, the children of its original note, and its descendants are the descendants of the original note. By contrast, this does not mean that aliases can now have their own discrete children/descendants.