We can achieve this by writing custom JS code. you can see the post on how an accordion works in this thread.

https://collaborate.pega.com/question/how-collapse-acordian-8-version#comment-760601

For your scenario, try below approach.

1. Create a non autogenerated HTML section in the class of the accordion section.
2. Embed that section with the below code in that Accordion section. The below code works by triggering the click event in the respective accordion index.

<script>
 function openaccordion(value) {
 	$("div[data-lg-child-id='" + value + "'] .header").trigger("click");
 }
</script>

    3. Call this function on the buttons like below.

    4. Provide index of the layout in the value param. ("2" opens the second layout of the layout group)

    5. Configure Run script event on buttons with the respective index.

I worked for me on Pega 8.4. let us know if it works for you !