Admin menus on realistic sites are cluttered, overwheming

[iandunn]

On a site with a moderate amount of customization, the admin menu can quickly become cluttered and overwhelming.

A few rough ideas:

1. organize items into categories that are collapsed by default (similar to Gutenberg's Inspector sidebar). The categories could be around workflows like Publishing and Configuring; something less abstract like Post Types and Plugins; etc. The workflows idea might be difficult to implement while maintaining back-compat, due to how the item ordering is implemented.
2. let the user hide items they don't use, similar to how dashboard widgets can be hidden via Screen Options.

[iandunn]

Example of cluttered admin menu

[TimothyBlynJacobs]

Related: #47012, #50539.

[iandunn]

Ah, I think #47012 covers this well, thanks!