Loss of design with a parameter in the route [CI4]

Basing on the base_url() you can handle it:

For example,

CSS: <link rel="stylesheet" href="<?php echo base_url('assets/css/backend.css');?>?ver=<?php echo time();?>">
JS: <script src="<?php echo base_url('assets/js/example-folder/example.js');?>" ></script>

// time function at the end of css file is to overcome cahce issue. Otherwise, you might not see the latest changes you have made on the css file.