I've seen in many youtube videos (e.g. this) that in the state view there is a button to concentrate development and make coring provinces cheaper. However, I cannot find that button when I play EU4. Which DLC do I need to enable it?
1 Answer
You need the latest big one - Leviathan. Here's the wiki page that lists all dlc and features they unlock
Also notice that you lose some portion of development. It's not just free cheaper cores. And the upcoming free patch is going to nerf that ability significantly
