They have a --dev shorthand for dev dependencies, but it seems the dependency group PEP is not final, so there isn't a standardized way of doing this yet.
And honestly, the one I need more is a test group for CI, for things like coverage reporting and whatnot. If I can get that and if having multiple package indexes works properly (i.e. it can check my private repo first, and then pypi), I can probably port our projects to uv, at which point it's an internal discussion instead of a technical one.