Here’s how to have the ability to expand all/collapse all panes within an Elementor accordion element:
Add an HTML widget and 2 buttons to your site. Give the Expand All button the CSS class, “expand-all”, and the Collapse All button the class, “collapse-all”
Add an HTML element to your page and paste in the code as shown below.
Voila, now when you click the buttons they expand/collapse as desired.