tabs option

Hi there,

By default, you should be able to switch back and forth between the tabs — you can see this if you temporarily switch back to the default Storefront theme:

Link to image: https://d.pr/i/hlpZIv

If you wanted to completely remove the Additional Information tab, you can do that by using the code in the doc that @apmwebdev sent:
https://docs.woocommerce.com/document/editing-product-data-tabs/#removing-tabs

add_filter( 'woocommerce_product_tabs', 'woo_remove_product_tabs', 98 );
function woo_remove_product_tabs( $tabs ) {
    unset( $tabs['additional_information'] );  	// Remove the additional information tab
    return $tabs;
}

However, keeping two of them expanded the way your theme is doing, and making one collapsible would require more than just a PHP snippet like we could provide here. If you need assistance with coding or custom development, we recommend reaching out to a developer from one of the services at https://woocommerce.com/customizations/