Move all non-core WordPress admin menu items to the bottom of the sidebar

organize-wp-admin-menu-sidebar.php

<?php
add_action( 'admin_menu', 'jp_reorder_admin_menu', 999 );
/**
 * Reorder wp-admin sidebar menus
 */
function jp_reorder_admin_menu() {
	global $menu;
	if ( empty( $menu ) ) {
		return;
	}

	// Core menu items and their default positions
	$core_items = array(
		'index.php'               => 2,      // Dashboard
		'edit.php'                => 5,       // Posts
		'upload.php'              => 10,    // Media
		'edit.php?post_type=page' => 20,  // Pages
		'edit-comments.php'       => 25,        // Comments
		'themes.php'              => 60,    // Appearance
		'plugins.php'             => 65,   // Plugins
		'users.php'               => 70,     // Users
		'tools.php'               => 75,     // Tools
		'options-general.php'     => 80,      // Settings
	);


	// Separate core and non-core items
	$non_core_items = array();

	foreach ( $menu as $key => $item ) {
		// Skip separators
		if ( $item[4] === 'wp-menu-separator' ) {
			continue;
		}

		// If this is not a core menu item, store it for later
		if ( ! array_key_exists( $item[2], $core_items ) ) {
			$non_core_items[] = $item;
			unset( $menu[$key] );
		}
	}

	// Add a separator after core items
	$menu[95] = array( '', 'read', 'separator-custom', '', 'wp-menu-separator' );

	// Add non-core items starting at position 120
	$position = 120;
	foreach ( $non_core_items as $item ) {
		$menu[$position] = $item;
		$position++;
	}

	// Sort the menu by key to ensure proper ordering
	ksort($menu);
}