How to draw nested nodes using Fletcher package?

Questions
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5

I can share the code in addition to the previews in the future.

and it makes the licensing of the code unambiguous

No, it does not. Many don’t even know the license here, not to say that all have to follow that license (if a link gets shared, the provided content, definitively does not fall under the forum license, if you mean that by unambiguous).
Any code snippet shared there can be used in binary or compiled form without any attribution. A user can add a license that adds the need for attribution.

I, in the future, will add the initial code:

#import "@preview/fletcher:0.5.8"

#fletcher.diagram(node-shape: rect, node-stroke: black, {
  import fletcher: edge, node

  node((0, 1), [Inner Node 1], name: <in11>)
  node((1, 1), [Inner Node 2], name: <in12>)
  node((.5, .5), [Outer Node], stroke: none, name: <on1>)
  node((0, 0), enclose: (<in11>, <in12>, <on1>), name: <enc1>)

  node((0, 3), [Inner Node 1], name: <in21>)
  node((1, 3), [Inner Node 2], name: <in22>)
  node((.5, 2.5), [Outer Node], stroke: none, name: <on2>)
  node((0, 3), enclose: (<in21>, <in22>, <on2>), name: <enc2>)

  edge(<enc1.south>, "-|>", <enc2.north>)
})