Remove configurable product from the cart, and only keep linked products.

linked-product--remove-configurable-product.php

<?php
// Prevent the linked items to be removed automatically when removing the main product
add_filter( 'mkl_pc/remove_linked_items', '__return_false' );

// Remove the configurable item from the cart, if the linked items were added to the cart.
add_action( 'mkl_pc/added_linked_product_to_the_cart', function( $cart_item_key, $product_id ) {
	WC()->cart->remove_cart_item( $cart_item_key );
	// Add custom notice
	wc_add_notice( '<a href="' . esc_url( wc_get_cart_url() ) . '" class="button wc-forward">' . esc_html__( 'View cart', 'woocommerce' ) . '</a>' . ' Din kjole design er blevet tilføjet til din kurv.' );
	// Prevent default notice 
	throw new Exception();
}, 20, 2 );