Assuming you are using a child theme (if not you’ll need to change the path for the script), you can try:

in your functions.php

function scripts_123qaz() {
    wp_register_script( 'sort_123qaz', get_stylesheet_directory_uri() . '/js/sort_123qaz.js', array('jquery'), '1.0.0', true);
    wp_enqueue_script( 'sort_123qaz' );
}
add_action( 'admin_enqueue_scripts', 'scripts_123qaz' );

Then in your theme, if you don’t have a js folder, make one and add the file named sort_123qaz.js and the contents of that file:

$(document).ready(function() {
	var $sort_123qaz = this;
	var $list_123qaz =  $('li#menu-settings ul.wp-submenu');
	var $listLi_123qaz = $('li',$list_123qaz);
	$listLi_123qaz.sort(function(a, b){
		var keyA = $(a).text();
		var keyB = $(b).text();
		return (keyB < keyA) ? 1 : 0;
	});
	$.each($listLi_123qaz, function(index, row){
		$list_123qaz.append(row);
	});
});

That will sort all the list items in the Settings flyout menu, alphabetically.

There are there ways to add this code but not knowing your theme, structure etc… this is the generic way.