Collapse Stack - Different names when open/closed

To display the entire content, I created a link (External) with a Uniqie ID and entered “Read More” as a comprehensible name. Works perfectly! But now I want a different, equally understandable name when the content is open, because it still says “Read More” and that is quite confusing. For example, “Close”. Is that somehow possible?

Thanks for the link. Where and how do I install this?