ng them by those values, the groups are sorted, then the items
    of each group are concatenated.
  {%- endcomment -%}
  {%- assign string_ordered_groups = string_ordered_pages
        | group_by_exp:"item", "item.nav_order | default: item.title | append:''" -%}
  {%- if site.nav_sort == 'case_insensitive' -%}
    {%- assign sorted_string_ordered_groups = string_ordered_groups | sort_natural:"name" -%}
  {%- else -%}
    {%- assign sorted_string_ordered_groups = string_ordered_groups | sort:"name" -%}
  {%