Theme switcher – No redirect to index.php

I’d like user to be able to change theme using the theme-switcher plugin, but without them being redirect to the index. I want them to stay on the page they are (I use WP2 as a CMS). I tried to change this myself but I have no big knowledge of php really…

I suppose I should change the part at the top that set the redirection and the structure of the url at the end (I don’t use the dropdown). The structure, I might be able to fix it myself, but I have no idea of the way to change the redirection, or if it’s even possible to set the cookie without going back to the index…

Thanks for your help!

(The theme-switcher code can be found there: https://dev.wp-plugins.org/file/theme-switcher/trunk/theme-switcher.php)