How do I bind Cascading Form data to a collection?

Task: when choosing a value from the # section drop-down list, the values in the # category drop-down list were selected according to the rule and saved in the corresponding fields of the collection.


Suggested solution from support: https://www.wix.com/velo/example/cascading-form

  1. Bulky
  2. Stops working when connecting a form to a collection

Please tell me how to solve this problem.