Duplicate links in a navigation structure

Does anyone know of any research or studies regarding usability concerns of duplicating links within a navigation structure? When I say “duplicating links” I mean repeating a menu item within the navigation as demonstrated below with “Child link 1”. Keep in mind SEO is not a concern in this situation since this is for an enterprise application.

  • Parent link 1
    • Child link 1
    • Child link 2
    • Child link 3
  • Parent link 2
    • Child link 4
    • Child link 5
  • Parent link 3
    • Child link 1
    • Child link 6