How to make cell for code generation?

The clip in https://docs.marimo.io/guides/editor_features/ai_completion.html#generate-code-with-our-ai-assistant shows cell enabled for code generation, but I don't see how to make cell for this generative mode, I mean where's the option to be turned on to allow cell for this? Marimo config:
.$ marimo config show
...
[ai.open_ai]
model = "qwen2.5-coder:1.5b"
base_url = "http://localhost:11434/v1"