Create conditional dropdown to choose country, city, distric, depend on choosing on previous choose on previous dropdown

Hi i see your youtube video 8 years ago. As attached, I think that idea was so good and easier for me to implement.

I didnt find that button, nor function like in the video https://youtu.be/nBrGFn8vvLk?si=Dd3N0SFhN_vvhEz6

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