What problem does this address?

Currently when creating a Navigation block a wp_navigation post is automatically created and all inner blocks are saved to that post.

It is therefore not possible to create a Navigation block that is local to a specific post context. This also means that anyone without the edit_theme_options capability cannot create Navigations even if they are only for the purpose of a single page (as opposed to global).

What is your proposed solution?

Add a means by which users an opt to save the Navigation block items locally to the current post. In such cases no Navigation Post would be created and the block would use standard uncontrolled inner blocks.

cc @spacedmonkey who has previously discussed this with me.