Hey,
We do have that culture available, but it seems that the set of internationalisation data loaded by the editor is missing it. That’s a bug on our part, sorry about that, we’ll get it fixed for 4.11.
In the mean time, you can delete the existing “icudt53l” folder in UE4\Engine\Content\Internationalization, and replace it with the “icudt53l” folder from UE4\Engine\Content\Internationalization\All. That will give you access to all of the cultures we know about.
You’ll also need to change your “Internationalization Support” setting to “All” to make sure that the data is packaged for your game. This can be found in your Project Settings, under the advanced settings in the “Packaging” section.
Thanks.