Despite the research requiring Chemical Science, it isn't a prerequisite on the tech tree.

I'm not really sure about changing this. I understand it would be more correct, but it has the unintended consequence of significantly changing the placement of the MK2 storage tank technology.

The current way makes the upgrade path very clear, because the mk2 storage tank is directly next to the standard storage tank technology. If I change it to require chemical science, the prerequisite link to the original storage tank is broken and it becomes a single node attached to chemical science.

More neatly organised tech tree vs technically correct prerequisites is a really tough decision to make if there aren't any other factors to influence it. I'm open to more discussion or feedback if you or anyone else has any thoughts.

Could you make it configurable? I definitely understand why you might want it the more stylistically appropriate way, and I'm entirely comfortable with that being the default setting.

Sorry I didn't get back to this sooner, life has been busy.

I've just updated the mod changing the prerequisite to chemical science.

I mulled it over a bunch and realised my reasoning for it being neater was silly. Since you can't research it until you get chemical science anyway, it makes more sense for it to be next to chem science on the tech tree, so that a player knows it is an option to research at that point.

Your idea to make it configurable is a good one. It's definitely possible, but now that I've changed the prerequisite to chemical science I'll keep things simple and leave it without an option for now.