A group of Microsoft Products and technologies used for sharing and managing content, knowledge, and applications.
Hi Matthew George (mgeorge),
I go through the post carefully. based on the description, you may achieve this with Microsoft Power Automate. You may Check the Power Automate blog for more information: Update a secondary SharePoint list using Flow - Power Platform Community (microsoft.com)
You may need to modify the flow example given in the link, if you need assistance on this. I would suggest you post in Microsoft Power Automate Community - Power Platform Community where you can get dedicated help.
Best Regards,
Clark