By default, Toolset Accordions made with Toolset Layouts will expand the first panel of an accordions cell.

This is as well the default in native Bootstrap 3.

If you want to have all Panels collapsed when you load the page initially, and only open each panel on click, you can add this JS to the Toolset > JS/CSS editor:

jQuery('[id^=ddl-panel_]').removeClass('in');

What we do with the code above is targeting every accordion body produced and remove the “in” class.
Since Toolset Layouts automatically generates the ID with a random number I used a wildcard to address the hardcoded Toolset Layouts Accordion body prefix:

ddl-panel_