Using Metafield Delivery Dates
EasyRoutes supports time window and delivery date information in order attributes. Metafields are not natively supported at this time but you can populate Shopify order information using Shopify Flow.
Shopify Flow allows you to create workflows that will run whenever a trigger events occurs. Workflows can contain actions including those that update orders. For example, you can structure a workflow like the following to update an order when it is created:

The "Send Admin API request" action contains a mutation that gives instructions on what the request should act on and the data it should use to perform the action. You can update an order's attributes using the "orderUpdate" mutation:
Once you select a mutation you need to specify how order data should be updated. An update like the following would replace the existing order attributes and insert a single attribute called "EasyRoutes" with a value of "testvalue":
{ "input": { "id": "{{order.id}}", "customAttributes": [ { "key": "EasyRoutes", "value": "testvalue" } ] } }
You can update the mutation to include delivery date and time information that are pulled from other order fields (including metafields). For the full list of attribute names and formats that are supported for delivery dates, see our support article for delivery date integration. For a list of attribute names and supported formats for time windows, see our support article on our support article on Time Windows.
Here's an example where the mutation is updated so that order attributes are replaced with a delivery date attribute that's populated from a metafield with the key "deliverydate".
{ "input": { "id": "{{order.id}}", "customAttributes": [ { "key": "Delivery Date", "value": {{order.deliveryDate.value}} } ] } }
Note that this example will replace all existing attributes on the order. You can find the metafield key used for the "value" using the "Add a variable" button when editing the mutation.
You can learn more about Shopify Flow on the Shopify Help Center.