Map popups can be configured using HTML which allows for a lot of creativity. However not all HTML tags are allowed (for security reasons I guess), but being able to use <details> and <summary> would be neat as it would allow users to hide / show (collapse) content in the popup. Thus, it would provide a better user experience for popups with a lot of content (e.g. images, histograms, tables etc.).
Example markup:
<details> <summary>Open for details</summary>Here is more information </details>
