Kroom wants to override something in another mod, not the Data folder.
This isn't really a scenario that occurred to me, and there's not a good way to do it right now. You can try using a path like %USERPROFILE%\Documents\My Games\Cosmoteer\Mods\Other_Mod\, but that will only work for players who haven't moved their Documents folder somewhere else.
Also, the order in which mods are loaded will probably affect this, and that's not something you can control right now. Mods are loaded in whatever order Windows gives Cosmoteer their folder names, which seems to be alphabetical, but alphabetical order can change depending on what language the player's operating system is set to.