in this moment with your Variation Swatches when for example one size of an shoes is out of stock is selectable, and only when client click on “add to chart” is write on pop-out ( Sorry, this product is unavailable. Please choose a different combination. ) in others plugin how you see in this link ( https://radiustheme.com/demo/wordpress/woopluginspro/product/woocommerce-variation-video-gallery/?attribute_pa_color=gray ) is make a X over the colors or size that is out of stock.. this is very important, i recived more negative feedback from my client of the actual system because is not visible the out of stock size of my product.