There’s this one, although I have no idea if it will work. It’s not in Shopify Workflow, it’s adding an input in your cart page. Give it a read:
Set custom issue, delivery and due dates - Sufio for Shopify
Something like this in order to add a default due date:
<input type="hidden" name="attributes[Invoice Due Date]" id="invoice-due-date" value="2020-11-13" />
Definitely read the article I attached above.