Hi,
That's a cool mod.

I just noticed that's the in game quality informations (acc. and max speed) aren't show for the locomotives.
Do you think it's possible to add it ?

Thanks in advance

I investigated a little further.

I suspected a potential conflict with ‘Hard Nauvis’, which also modifies locomotives, but the problem persists even when removing this mod.

I also noticed that the storage tank is also missing the information. Whereas both types of wagons display it correctly.

This isn't easily possible due to engine limitations.

To add quality scaling for parameters that don't usually scale, I internally use different entity prototypes for different qualities. However, to keep recipes working normally, those all share the same item prototype - and the item is what you are usually looking at for quality information.
I could add all the quality information to the item description, but that would make the descriptions very long (eg. if locomotives specified max speed, acceleration, fuel consumption for every single quality).

The wagon capacity scaling is something that's already implemented in the engine, so it isn't affected by the same limitations as other parameters.

I could request a mod interface from the factorio developers, but I'd have to think about how that should work, and there is no guarantee that they decide to implement it (especially before the release of 2.1).