Display debugging state (enabled/disabled) in the ClassicPress admin bar

functions.php

function codepotent_debug_notifier_register_admin_bar() {

	// ...adjust the permission to suit your needs.
	if (!current_user_can('manage_options')) {
		return;
	}

	// Bring the admin bar into scope.
	global $wp_admin_bar;

	// Assume debugging is disabled; set an appropriate text label.
	$label = esc_html__('Debugging Disabled', 'codepotent-debug-notifier');

	// Check if debugging is actually enabled; if so, reset the label.
	if (defined('WP_DEBUG')) {
		if (WP_DEBUG == true) { // Loose comparison is intentional here.
			$label = '<div style="color:#f00;">'.esc_html__('Debugging Enabled', 'codepotent-debug-notifier').'</div>';
		}
	}

	// Add the admin bar entry.
	$wp_admin_bar->add_menu([
		'parent' => false,
		'id'     => 'codepotent-debug-notifier',
		'title'  => $label
	]);

}
add_action('wp_before_admin_bar_render', 'codepotent_debug_notifier_register_admin_bar');

// Related discussion: https://forums.classicpress.net/t/show-error-notice-in-admin-when-debugging-is-enabled/2921