Reordering and removing left admin menu items

Clone the administrator user role

//https://www.kvcodes.com/2015/04/wordpress-clone-user-role-to-create-new-role/
//https://nazmulahsan.me/clone-or-add-new-user-roles/
add_action('init', 'cloneUserRole');
function cloneUserRole()
{
 global $wp_roles;
 if (!isset($wp_roles))
 $wp_roles = new WP_Roles();
 $adm = $wp_roles->get_role('administrator');
 // Adding a new role with all admin caps.
 $wp_roles->add_role('client', 'Client', $adm->capabilities);
}

Modify the newly cloned user

// https://www.wpmayor.com/how-to-remove-menu-items-in-admin-depending-on-user-role/
add_action( 'admin_init', 'my_remove_menu_pages' );
function my_remove_menu_pages() {
global $user_ID;
if ( current_user_can( 'client' ) ) {
remove_menu_page( 'tools.php' ); // Tools
 remove_menu_page( 'users.php' ); // Users
 
 remove_submenu_page( 'index.php', 'update-core.php' ); // Dashboard - Updates
 remove_submenu_page( 'edit.php', 'edit-tags.php?taxonomy=post_tag' ); // Posts - Tags 
 
 remove_submenu_page( 'themes.php', 'theme-editor.php' ); // Appearance - Editor
 remove_submenu_page( 'plugins.php', 'plugin-editor.php' ); // Plugins - Editor
 }
}

Activate a new user role through a plugin.

I am working on a custom functions plugin I call AWP Custom Functions (Advanced WordPress  https://www.facebook.com/groups/advancedwp/ as it was Devin Walker through AWP who first got me hooked on the concept of a custom functions plugin. )

To activate a new user role through a plugin add something like the following code to your main plugin file.

// On plugin activation create following user role.
 //https://codex.wordpress.org/Function_Reference/add_role
 // https://codex.wordpress.org/Function_Reference/register_activation_hook
 // FILE = path to the main plugin file inside wp-content/plugins directory. A full path will work.
 // function: rename it to plugin file name.
 function awpcustomfunctions_activate() {
 add_role( 'custom-client', 'Custom Client',
 array(
 'read' => true ) );
 }
 register_activation_hook( __FILE__, 'awpcustomfunctions_activate' );

Reordering the left admin menu

/*********************
* re-order left admin menu
**********************/
function reorder_admin_menu( $__return_true ) {
    return array(
         'index.php', // Dashboard
         'edit.php?post_type=page', // Pages 
         'edit.php', // Posts
         'upload.php', // Media
         'themes.php', // Appearance
         'separator1', // --Space--
         'edit-comments.php', // Comments 
         'users.php', // Users
         'separator2', // --Space--
         'plugins.php', // Plugins
         'tools.php', // Tools
         'options-general.php', // Settings
   );
}
add_filter( 'custom_menu_order', 'reorder_admin_menu' );
add_filter( 'menu_order', 'reorder_admin_menu' );

Removing top level and sub menu left admin menu items.

Reordering left admin menu WordPress

/*
* Remove top level and sub menu admin menus
*/
function remove_admin_menus() {
   remove_menu_page( 'index.php' ); // Dashboard
   remove_menu_page( 'edit.php' ); // Posts 
   remove_menu_page( 'upload.php' ); // Media
   remove_menu_page( 'edit.php?post_type=page' ); // Pages
   remove_menu_page( 'edit-comments.php' ); // Comments
   remove_menu_page( 'themes.php' ); // Appearance 
   remove_menu_page( 'plugins.php' ); // Plugins 
   remove_menu_page( 'users.php' ); // Users 
   remove_menu_page( 'tools.php' ); // Tools
   remove_menu_page( 'options-general.php' ); // Settings 
}
add_action( 'admin_menu', 'remove_admin_menus' );

// Remove sub level admin menus
function remove_admin_submenus() {
   remove_submenu_page( 'index.php', 'update-core.php' ); // Dashboard - Updates
   remove_submenu_page( 'edit.php', 'post-new.php' ); // Posts - Add New Post
   remove_submenu_page( 'edit.php', 'edit-tags.php?taxonomy=category' ); // Posts - Categories
   remove_submenu_page( 'edit.php', 'edit-tags.php?taxonomy=post_tag' ); // Posts - Tags
   remove_submenu_page( 'edit.php?post_type=page', 'post-new.php?post_type=page' ); // Pages - Add New Page
   remove_submenu_page ( 'upload.php', 'media-new.php'); // Media - Add New

   remove_submenu_page( 'themes.php', 'themes.php' ); // Appearance - Themes
 
//- Not working. Uses other code. See further below.
   remove_submenu_page( 'themes.php', 'customize.php' ); // Appearance - Customize
   remove_submenu_page( 'themes.php', 'widgets.php' ); // Appearance - Widgets
   remove_submenu_page( 'themes.php', 'nav-menus.php' ); // Appearance - Menus
 
//- Not working
   remove_submenu_page( 'themes.php', 'customize.php' ); // Appearance - Header

//- Not working
   remove_submenu_page( 'themes.php', 'customize.php' ); // Appearance - Background
   remove_submenu_page( 'themes.php', 'theme-editor.php' ); // Appearance - Editor 
 
   remove_submenu_page( 'plugins.php', 'plugin-install.php' ); // Plugins - Add New Plugins
   remove_submenu_page( 'plugins.php', 'plugin-editor.php' ); // Plugins - Editor
 
   remove_submenu_page( 'users.php', 'user-new.php' ); //Users - Add New User
   remove_submenu_page( 'users.php', 'profile.php' ); //Users - Your Profile
 
   remove_submenu_page( 'options-general.php', 'options-writing.php' ); // Settings - Writing
   remove_submenu_page( 'options-general.php', 'options-reading.php' ); // Settings - Reading
   remove_submenu_page( 'options-general.php', 'options-discussion.php' ); // Settings - Discussion
   remove_submenu_page( 'options-general.php', 'options-media.php' ); // Settings - Media 
   remove_submenu_page( 'options-general.php', 'options-permalink.php' ); // Settings - Permalink
}
add_action( 'admin_init', 'remove_admin_submenus' );

Removing Appearance -> Background and Header submenu pages require another function.
I found the code here: https://wordpress.org/support/topic/remove-header-and-background-option-pages-in-twenty-eleven-child-theme?replies=11

//Remove the custom options provided by the default twentyeleven theme. 
add_action( 'after_setup_theme','remove_header_background', 100 );
function remove_header_background() {
 remove_custom_background();
 remove_custom_image_header();
}

RemovingAppearance -> Customize also requires a new function.
I found the code here: https://wordpress.org/support/topic/remove-customize-from-admin-menu?replies=5

function remove_customize_page(){
 global $submenu;
 unset($submenu['themes.php'][6]); // remove customize link
}
add_action( 'admin_menu', 'remove_customize_page');

/* Add submenu item to another submenu - One big problem. The moved submenu link will open in th e original location. I used upload.php as an example on adding the media library. Check above in the remove_submenu_page for other options. */
function add_submenu_item() { 
 // Resource page: https://clivern.com/adding-menus-and-submenus-for-wordpress-plugins/
 // add_options_page($page_title, $menu_title, $capability, $menu_slug, $function);
 
 add_dashboard_page('page-title', 'submenu title', 'manage_options', 'upload.php');
 add_posts_page('page-title', 'submenu title', 'manage_options', 'upload.php');
 add_media_page('page-title', 'submenu title', 'manage_options', 'upload.php');
 add_pages_page('page-title', 'submenu title', 'manage_options', 'upload.php');
 add_comments_page('page-title', 'submenu title', 'manage_options', 'upload.php');
 add_theme_page('page-title', 'submenu title', 'manage_options', 'upload.php');
 add_plugins_page('page-title', 'submenu title', 'manage_options', 'upload.php');
 add_users_page('page-title', 'submenu title', 'manage_options', 'upload.php');
 //Tools
 add_management_page('page-title', 'submenu title', 'manage_options', 'upload.php');
 //Settings
 add_options_page('page-title', 'submenu title', 'manage_options', 'upload.php'); 
}
add_action( 'admin_init', 'add_submenu_item' );

new menu – left admin

// submenu item to top level menu 
// add_menu_page( $page_title, $menu_title, $capability, $menu_slug, $function, $icon_url, $position ); 
 // https://gist.github.com/hofmannsven/8269251
function new_menu() { 
 add_menu_page('page-title','menu-title1','manage_options','widgets.php', '', 'dashicons-desktop');

// Submenu to new submenu -- It will still open in the original area.
 // add_submenu_page($parent_slug, $page_title, $menu_title, $capability, $menu_slug, $function);
 add_submenu_page('widgets.php', 'page-title', 'menu-title2', 'manage_options', 'upload.php'); 
}
add_action( 'admin_init', 'new_menu' );

I filled out three trac tickets. One for admin_menu not removing the theme editor 32784 the other for lack of consistency in removing submenu items 32785. The third when removing submenu item and then adding it to another existing top level menu clicking the moved submenu item will open it in the original location 32788.

I wrote a tutorial on adjusting the top admin tool bar menu.

Additional resources:
https://www.paulund.co.uk/add-menu-item-to-wordpress-admin
https://tommcfarlin.com/add-a-separator-to-the-wordpress-menu/
https://markwilkinson.me/2014/11/altering-wordpress-admin-menus/

https://codex.wordpress.org/Function_Reference/remove_menu_page
https://wordpress.stackexchange.com/questions/52099/how-to-remove-entire-admin-menu

Plugins:
https://wordpress.org/plugins/codepress-admin-columns/
https://wordpress.org/plugins/admin-menu-editor/