Shopify Flow

Awesome app. My complaint so far is that dealing with order fulfilments can be really tricky. It's just not intuitive, and half the things I want to do I just can't figure out. Like I was trying to items in an order into different fulfillments. I wanted to put the preorder items seperate from the instock items so that the instock items could be shipped now. I couldn't figure out how to do it, and ended up having to write some code to edit the orders via the shopify api myself..