Found it on Nexus. Thank you very much!

@Thor
You the first who I know, who has this weird problem.
Nexus Version [www.nexusmods.com]

I launched/started the game several times but couldn't find this in the extension list at all. I couldn't find it, among the other mods, from the mod name, your name, or the date sorting. I also tried re-subscribing many times but the results were the same.
I'm not new to steam mods but this is the first time I encounter something like this.
Would you consider uploading to Nexus mod? It's easier to organize mods there.

@Thor
It loads fine, you just need to lunch the game.
The X4 mods are updated and downloaded automatically right before the game starts.

Could you please re-upload? Not sure why but nothing happened after subscribing. Nothing is loaded to my computer.