The SaaS version of Label Studio does have a natural language interface to create custom interfaces: https://docs.humansignal.com/guide/ask_ai

I'm ostensibly an expert in the product and I probably use that 90%+ of the time (unless I'm testing something specific) -- using a sketch as input is a cool idea though!

Disclaimer: I'm the VP Product at HumanSignal the company behind Label Studio.