Is it possible to reference the copyright field found in design configuration within the footer section? I've checked here https://docs.magento.com/m2/ce/user_guide/marketing/variables-reference.html with no luck. I would ultimately like to add it to my email footer.
The copyright footer variable which you specified is currently not available in email variables. However You can add your own custom variable refer the below link. https://docs.magento.com/m2/ce/user_guide/marketing/variables-custom.html
I tried to add it in my system as shown in the below screenshots.