Hi @Zachary Willard,
Thank you for posting in this community.
According to your description, I have tested it. SharePoint currently does not support automatically populating metadata of master files on subfolders. This is designed by SharePoint.
Unfortunately, you can only add metadata manually.
You can also provide feedback on this feature here. This helps the development team notice the feature and make it more likely to be implemented. Your contribution is highly appreciated.
Thank you for your kind understanding.
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