Yes, you can attach parameters orderNumber and orderEmail to your regular returns portal URL.
orderNumber: can contain the order number or order name on Shopify
orderEmail: contains the email address used in the order
A fully working URL looks like the following https://returns.richcommerce.co/return/new?c=healthyfoodcompany&orderNumber=16347&orderEmailemail@example.com
Note that characters have to be escaped correctly to be URL scheme compliant. See Shopify's documentation on Liquid about url_escape and url_param_escape here.
Use cases for the URL
your Shopify customer accounts page
your Shopify order confirmation emails
your helpdesk in case reps should be able to initate returns as well