Hot on the heels of Stellaris, Paradox's Second World War grand strategy Hearts of Iron 4 is arriving June 6. In the latest developer diary, PDS has revealed that Hearts of Iron 4 will be its "most moddable game yet", and walks us through a suite of mod-friendly features and tools.
Giving modders the freedom to insert the houses of Westeros into Operation Overlord has required that next to nothing be hard coded. "HOI3 had a lot of hard coded logic and references to certain nations. In HOI4 all these things are in soft code, or part of scenario script setups making it a much better platform for cool mods."
Meanwhile, the inbuilt mod tool will make creating new mods and playing with the soft code easier. Launching the game in debug mode reveals additional visual modding tools such as the 'Nudger', a GUI for modifying map properties on the fly, and with real-time error feedback at that. When you're done, there's a one-click upload process to get it up on the Steam Workshop.
On the more technical end, PDS' scripting language has been cleaned up and made more user friendly thanks to progress in its other series. Lua scripting for AI has been thrown out the window. The official rundown is full of examples that I can't pretend to follow being good only for playing mods, so if you have the skill to create your own, I highly recommend you have a read.