Make Sitemap collapsible

Hi Tony,

I have been using the WP-Sitemap plugin you designed and it’s very clean and simple and works really well.

My sitemap is long and I would like to ask a question: is there a way to make it collapsible? I can work around the CSS part but I really don’t dare to touch the code as I am not really knowledgeable.

I found this page: http://bernholdtech.blogspot.de/2013/04/very-simple-pure-css-collapsible-list.html and seems very simple but I do want to ask your advise on how to implement it on the plugin.

I would also want to ask you if there is a way to save the data somehow because I have quite a few pages that I have hidden but the other day that I had to deactivate the plugin I lost it all.

Thanks in advance!

https://ww.wp.xz.cn/plugins/wp-sitemap-page/