Hi @Heidi Heider,
Thank you for posting in this community.
Are you trying to figure out how to manage file templates added via the New button?
You can manage your uploaded ones directly through the Edit New menu.
Or maybe you want to know where the file templates are stored in the library?
They are stored in the Forms folder of the library.
Open the library in File Explorer to see the Forms folder which contains the file templates for the library.
Please follow this article to configure how to open SharePoint Online document libraries in File Explorer:
SharePoint Online: How to Enable “View in File Explorer” in Microsoft Edge?
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