How can I alias a given extension (.ttx) to a desired syntax (XML)?

[frankrolf]

I am working with .ttx files, which use XML syntax.
mdls recognizes a ttx file as follows:

kMDItemContentType                 = "org.fonttools.ttx"
kMDItemContentTypeTree             = (
    "org.fonttools.ttx",
    "public.xml",
    "public.text",
    "public.data",
    "public.item",
    "public.content"
)

I followed the instructions for “settings for plain files”, but I am not certain this is the right place to achieve what I am after.
Here is what I tried (which might be completely wrong – sorry):

What would I need to do to achieve what I’m after?
A PR perhaps, like here? db30a2c

Thanks!

[sbarex]

It is not possible. It must be done during compilation.

That panel is only used to manage files WITHOUT EXTENSION.

[frankrolf]

Along similar lines – would it be possible to imagine something like UTI type “forwarding”?

Let’s say I have my own custom UTI, which is based on another one (like in this case) – perhaps I could help the app understand that I’d like to preview type x as type y? Or alternatively, just have a list of UTIs to be treated as plain text? Would definitely beat the QuickLook icon preview.

[sbarex]

UTI management is completely delegated to the operating system. It is the operating system that evaluates which quicklook extension to invoke based on whether it supports that particular UTI. So if the app has not been compiled declaring support for that format it will never be invoked.