Announcing new file template management for document library content types

Can anyone advise where these new templates are actually stored?  They dont seem to be visible in the /forms URL under the library, but when you edit one through the new UI, it reports as being there through its file location?

I want to rename a file that was loaded as a template.  I have edited it in the new UI, and used Save As with the new name, but this doesn't; show up.

I suspect the only approach at the moment is to delete the new template, and then add one with the modified name? = No.  I tried this after having tried the Edit and Save as above, and on adding the new template, got a "this document exists, do you want to replace it warning", to which I responded replace.  The new template appears to upload correctly, but never appears in the +New list, or when you edit the +New list.   

So it seems, as with so many of these changes, it is not ready for prime time, but cant be turned off and cant be fixed if you dont do it perfectly the first time.   It is increasing getting very difficult to justify to the executive (and more so to savvy end users) why we use microsoft products......