change-dlm-upload-folder.php

gistfile1.txt

<?php

add_filter( 'upload_dir', 'change_upload_dir_for_dlm', 30 );
function change_upload_dir_for_dlm( $pathdata ){
	
	if ( isset( $_POST['type'] ) && 'dlm_download' === $_POST['type'] ) { 
		if ( empty( $pathdata['subdir'] ) ) {
			$pathdata['path']   = $pathdata['path'] . '/private';
			$pathdata['url']    = $pathdata['url'] . '/private';
			$pathdata['subdir'] = '/private';
		} else {
			$new_subdir = '/private' . $pathdata['subdir'];

			$pathdata['path']   = str_replace( $pathdata['subdir'], $new_subdir, $pathdata['path'] );
			$pathdata['url']    = str_replace( $pathdata['subdir'], $new_subdir, $pathdata['url'] );
			$pathdata['subdir'] = str_replace( $pathdata['subdir'], $new_subdir, $pathdata['subdir'] );
		}
	}

	return $pathdata;
	
}