Badges based on User Custom Fields?

ah - the answer is to add .json to the URL and you will find the ID there. e.g.

/admin/customize/user_fields.json

hat tip to @simon who explains it in this post: Querying user_custom_fields - #2 by simon

sometimes spending a little time searching existing topics on meta will turn up the answer to your questions. Many people have come before you who share your goals.

You’re right. And thanks for the tip!