We would like WooCommerce Pre-Order to allow mixed cart orders, which also includes in stock products?

A tick-box per product would be great to allow mixed cart.

Mixed cart warning pop-up alerts your shoppers when they have both pre-order and in-stock items in the same cart.

We have moved across from Shopify where we were using https://apps.shopify.com/preorder-now. It is very similar to this extension, but also allows mixed carts.