See https://www.mediawiki.org/wiki/Manual:Collapsible_elements.
The default toggle text is Expand/Collapse.
The Header | remains visible |
---|---|
This content | is hidden |
at first | load time |
If one wishes something different, data-collapsetext= and data-expandtext= may be set as in this example:
The Header | remains visible |
---|---|
This content | is hidden |
at first | load time |