First of all, this tool is fantastic!
One observation, however, is that the tool comes from the perspective of the builder, not the consumer. Although this tool is essential for builders to create content that is tagged correctly with the right BCP-47 code, that use will potentially be dwarfed by consumers who will use it to select content in their language.
This impacts the following two aspects of the dialog, which are not relevant for consumers, but only builders:

