It was the second part of recrutation process. The first one was to create back-end API which should save data to JSON file. The front-end part is simple UI to comunicate with the back-end. I used React (Create React App, TypeScript version) and its Context API to manage global state. Nothing fancy. I also used Styled Components, but frankly speaking I didn't need it. UI is not complex or beautiful anyway.
In the app you can create new flows and remove them. Enjoy! It is deployed