Hide a specific action button conditionally in Woocommerce admin Orders list

I Would like to add some CSS to the order admin page to hide a custom order action button, but only if the order contains only downloadable products.

This is the function I need to load conditionally:

add_action( 'admin_head', 'hide_custom_order_status_dispatch_icon' );
function hide_custom_order_status_dispatch_icon() {
    echo '<style>.widefat .column-order_actions a.dispatch { display: none; }</style>';
}

Is that possible?

With CSS it's not be possible.

Instead you can hook in woocommerce_admin_order_actions filter hook, where you will be able to check if all order item are downloadable and then remove the action button "dispatch":

add_filter( 'woocommerce_admin_order_actions', 'custom_admin_order_actions', 900, 2 );
function custom_admin_order_actions( $actions, $the_order ){
    // If button action "dispatch" doesn't exist we exit
    if( ! $actions['dispatch'] ) return $actions;

    // Loop through order items
    foreach( $the_order->get_items() as $item ){
        $product = $item->get_product();
        // Check if any product is not downloadable
        if( ! $product->is_downloadable() )
            return $actions; // Product "not downloadable" Found ==> WE EXIT
    }
    // If there is only downloadable products, We remove "dispatch" action button
    unset($actions['dispatch']);

    return $actions;
}

Code goes in function.php file of the active child theme (or active theme).

This is untested but should work…