I need to create a page or post hierarchy

If all you need is to show the hierarchy in the menu, choose Appearance->Menus and build your hierarchy there by using Custom Links.

Use # for levels that don’t need to have a page, but use a URL when you get to the bottom level (a page that has content).

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You can then arrange them on the right then drag them to the right to create the hierarchy like this.

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Another option would be to setup categories to replicate your hierarchy like this.

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