Currently this task does not explain well why this task was created. It proposes a solution to an underlying problem that still needs to get defined. Knowing the background of the request in this task might provide better insight and lead to better solutions.

Also, which project is this task about? Is this about MediaWiki core, or some extension? What are examples for "collapsible elements"?

Please see https://mediawiki.org/wiki/How_to_report_a_bug for future tasks. Thanks!