A collapser is a widget that can be collapsed or expanded by a user. It contains a summary part which is always visible, and a details part which is only visible when the collapser is expanded. Collapsers are similar to HTML’s <details> and <summary> tags.
You can make a collapser:
Show details
You can put any widgets in a collapser:
Widgets
Note that anything you enter into the input widgets above persists when you open and close the collapser; that is because collapsers don’t delete the details, they just hide them.