how to customize the default #adminmenu in wp-admin

Question

i want to customize the #adminmenu for the wp-admin, how can i target the class via plugin?

im planning to use below function, but im not sure if this is the correct way of doing so..

add_action('admin_head', 'custom_nav');
function custom_nav(){
    include 'css/customNav.css';
}

//inside customNav.css
  #adminmenu { //insert styles here }

the main change i want, to make it horizontal across the browser and probably customize it by changing some colors, adding some new pages/links, remove unnecessary stuffs to it and so on..

Answer 1

You can't include 'css/customNav.css'; but you can try wp_enqueue_style.

The changes you are suggesting are not easy. You can add menus but changing the layout is impossible without rewriting the core.