openproject/app/views/projects/_hierarchy_header.html.erb

<th id="project-table--hierarchy-header">
  <div class="generic-table--sort-header-outer">
    <div class="generic-table--sort-header">
      <a title="<%= t(:label_sort_by, value: "\"#{t(:label_project_hierarchy)}\"") %>"
         <%= href_only_when_not_sort_lft %>
         class="<%= deactivate_class_on_lft_sort %>">
        <op-icon icon-classes="icon-hierarchy"></op-icon>
      </a>
    </div>
  </div>
</th>