Add a new field to the checkout; Add that new field to the order.
WooCommerce Code Reference
generation strategy and Premmerce WooCommerce Product Filter Plugin for managing
Get Order items and WC_Order_Item_Product in WooCommerce 3 · How ...
Adding a WooCommerce custom order action is pretty
If you notice what is going on, WooCommerce automatically generates hooks per action item in the order actions array. There might be several ...
For this three possibilities: If you really want to do it on order place you would have to use the hook: woocommerce_new_order. However I ...
do make available a list of all WooCommerce actions, filters and hooks. However, it's ...
Stumbled on this looking for the same thing which I've now figured out ( Woocommerce 3.x)... add_filter( ...
Filter hooks can pass several variables. For that case, you need to set additional parameters inside the add_filter function in order to access it.