So, i have all the dlcs and the base game here on gog, and i have the base game on steam, theres a way for me to use the dlcs from gog on my steam stellaris?

No, games bought on GOG do not unlock anything on Steam.

Was that an answer to the question? To me, unlock means unlocking a downloadable item in steam. Running the DLC installer on the base game in the steamapps directory is what I would try, if i were to buy Utopia, but not Stellaris, right now on GOG.

You could maybe do something similar for some games in theory, including Stellaris seeing how their DLC unlock system works. But GOG does not let you buy a DLC when you do not own the base game.

yes it was an answer and no you can not use a Gog DLC to add to a Steam Stellaris... they are different code for a start and its not legal in the end

the only way is to make use of the store unlock system which Steam and Gog both allow (from time to time) when Paradox aggres to special sales

I was entertaining the idea that you could actually register steam/gog purchases on paradox site and then have access to a mix of DLCs from either store. Not sure if all the functionality there yet, though.

It would not help ;)
As I posted earlier, you can not buy DLC on GOG for a base game you do not own.

well, I happen to own Stellaris on both, so it's a none-issue for me.