Hi Martin,
ohhhh, apologies now I read it again and got ya.
Unfortunately, this feature is not yet possible. Our team is already working on a massive Export add-on that will be the core of any export import features in the future. We need to get this done before we move into doing bulk upload. It is a very complex thing and we need to fight with ongoing WooCommerce code changes.
I am afraid you will need to do this step by step.
Hope that is possible.
Pavel