We are using SpaceExploration with all dependencies and this mod just doesnt enable the waterfill at all. Tried all "optional" dependencies.
Or do i have to play a FULL new game? ...

I will look in to this.
As i know factorio applies the information on launching the game so even if you load in a save it should take over changes to recipe, technology etc. most likely i have just set some value somewhere wrong preventing the game from unlocking it correctly.

Its really awkward because no Waterfill Mod works.
Even if i start a whole new game it doesnt work and that just dont make sense ^^"

if you mean that my mod doesnt work together with others as intended, thats something i can look in to.
if you mean that none of the other mods you tried work either then most likely something is going wrong outside of my control. i cant judge what exactly is going wrong when factorio doesnt behave as expected without seeing an error log if any errors have occured.
There might be a bug somewhere that breaks something accidentally but i cant tell whats the cause or what i can do to fix it if i dont have the details on what happened.

Ya. I tried all of your optional Dependency-Waterfill mods and none of them worked sadly.

I am playing with several different mods like SpaceExploration, AlienBioms, 248k, AAI Industry and many other QOL mods.
But only SpaceExploration should have this... "feature" to disable Waterfill.

But thanks for your answer ! Hope this does not make too much work.

i had a a look over the mod and i recently updated the mod to fix an issue where the tiles added where not unlocked correctly, so if your not on the most recent version i would ask you to update, as far as i can tell also all support for the optional dependency are set up as intended.
So in my end i have made no mistake and it should behave properly.
Its worth checking if one if the mods your using maybe lists water fill mods as a conflict which would cause factorio to disable them and that could be a possible explanation here.
besides 248k (where i dont know the mod) and maybe some of your QOL mods we have mostly a similar in regards of mods that change the content or other mods.
Since it works for me, what you can do is compare lists what i have added in my playthrough (modpack can be found on my profile) and which one you have, seems like one of the mods your using is causing the issue which means im unable to help you unfortunately.
If you ask the modders who made the mods you find not to be used by both of us, maybe they can help you out there. as much as i sometimes would like to do it, unfortunately i cant go around and "fix" other peoples mods. unless of course the bug in the interaction between my mod and there mod is caused by mine but that should really not be the case.

Could it be Krastorio2?

i do know about krastorio2 and have a general understanding on what its about but i have no idea bout its code and if it contains the ability to delete or disable something, if your suspecting one of the mods could have caused it you should contact the author of that mod.

Okay, thanks for your help and lifetime :)