Gets the selected items as stored (V, inheritable): one text string, or an array of them; empty when nothing is selected.
public IReadOnlyList<string> Values { get; }
ISO 32000-2 §12.7.5.4. Writers store the export value, though the clause names the displayed text for an
[export display] option; SelectedIndices matches either. An empty string, which some writers store for
"nothing selected", is not an item.