Easy methods to add taxonomy to Customers menu in admin?

I need to create a taxonomy that’s associated to the customers, subsequently I would like to indicate the taxonomy beneath “Customers” menu inside wordpress admin.
In codex there is a point out you could connect taxonomy to “nav_menu_item” however I am unable to discover any working instance of how this works. If I exploit:

register_taxonomy( 'experience', array( 'nav_menu_item' ), $args );

or

register_taxonomy( 'experience', array( 'customers' ), $args );

it would not work.

Any assist could be a lot appreciated.