I just started a Nullius playthrough. I only see "One-way valve 1" (and 2 later on in the tech tree) for valve options, no overflow or top-off valves. I have the configurable-valves mod installed as per requirements, but don't seem to see any research or graphics similar to it.

Am I missing something, or a bug?

Every pump can be configured into a valve. Check the mod controls to see the key bindings and reconfigure them if you prefer.

Ah thank you! It was the pumps!

It's done this way because the constraints of the 2.0 fluid system kind of put us in a corner. The built-in valve type they added resets extents like a pump but uses no power, so if it also has infinite throughput it really makes pumps useless. But if it has finite throughput you wouldn't want to use valves late game. So you'd kind of need tiers of valves multiplied by different types of valves, which is a whole mess. The best option is to have them have precisely the same throughput and power consumption as an equal tier of pump, and to avoid clutter of different tiered items, make them just be settings for the pump.

You can blueprint a pump configured into an overflow valve and put that on your hot bar to have it behave a bit more like a separate item if you find that interface more convenient than placing it and configuring it in separate steps.

Thanks anachrony for the excellent mod :)

I figured it was somewhere and I just wasn't seeing it (or was missing a mod or something along those lines).

I was excited to see Nullius available for Factorio 2.0 (saw on Dosh's videos on youtube). I had tried it pre-2.0, but didn't finish it (can't remember why). Giving it a run through now, excited!

Would you be interested in something like some code contributions for the Tips&Tricks section so noobs like me can have info in-game to search, and not bother everyone here? I'd be happy to contribute.

Couldn't hurt. I doubt the questions would stop, since some people will disable those, but it might help a portion of the playerbase. For valves, I think the best option will be to add a checkpoint where you just have to configure a valve to proceed. That's how we make sure people notice how to configure power priorities, but the 2.0 valve changes are newer and still have some rough edges. If you'd like to contribute toward development of some aspect of the mod, the best place to discuss that is on the Discord (linked on the Information Tab).