You already know about where lock files stand (and if I’m wrong and you don’t, message me). As for more standardization, it might be interesting to look at what Poetry, Hatch, pipenv, PDM, and even Flit offer out-of-the-box and see where their feature sets overlap. That’s probably the most telling as to what we might be able to to get the community to rally around standardizing.
This was proposed at Adding a non-metadata installer-only `dev-dependencies` table to pyproject.toml .
That stems from Core metadata specifications - Python Packaging User Guide which explicitly reserves test and doc for this sort of thing (and which I believe @barry has said he wished were plural 
). That makes it the closest we have to a standard around specifying development dependencies