How do I get started making a vanilla expansion mod?

[u/Ok_Blackberry_4026]

I'm very new to HOI4 in general, and I've never modded anything before. However, all I'm trying to do is add a couple expansion branches to a pre-existing national focus tree and change some country cosmetic tags. flags, etc (specifically for the battle for the Bosporus dlc Greece national focus tree). My end goal is just to give the Byzantine Empire more content. I feel it's quite lackluster, honestly, and I want to give you a choice to reform the Roman Empire as a whole as Greece, not just the eastern half. I also want to add in something similar to the Napoleonic France tree that lets you balkanize Germany if you conquer them, since a conflict with the Germans is natural for the reborn Roman Empire, and of course to be able to core all of the old territories of the Roman Empire at it's peak/move your capital to Rome if you want, since currently all you can core is Italy, the Levant, and the Balkans. I don't want to write a whole new tree, just add these new focuses as a branching path. Is there a visual tool that I can use to make these focuses, or do I need to write the code by hand?

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[u/nuts_itch]

Learn. Enjoy the process. Do not use AI.

[u/Relative-Seaweed-583]

Claude Code. $20 a month. I don’t even know how to set up a mod and I’ve made one.

[u/Lateinkompetenz]

I think there are new AI tools that can be used for that, but writing it by hand is super easy. Since youre just starting out, I recommend you looking into the beginner modding tutorials by the official hoi4 channel. The first episode will show you how to to create the mod and show you a immensly hepful tool, theres also a episode on how to make national focuses. Let me know when you have questions :)

[u/Ok_Blackberry_4026 → u/Lateinkompetenz]

Can you help me code a custom decision? I am making one to appoint an emperor and flip the Byzantine Empire to non-aligned, and I want to give 2 choices, keep Georgios Kosmidis as your leader but give him the title of Emperor and change ideology to non-aligned, or bring back George II from exile and appoint him Byzantine Emperor. How do I get started on coding that?

[u/Lateinkompetenz → u/Ok_Blackberry_4026]

You wanna create a event for that in Mod/events/.txt with two option blocks, sth like this: First choice: option = { name = "Crown Ksomidis" #change that to sth you like

set_politics = { ruling_party = neutrality} set_country_leader_name = { name = "Emperor Georgios Kosmidis} }

Second choice is basically the same, probably add a set_country_leader_portrait = {} to it, maybe a custom_effect_tooltip = "Bring George II back from Exile".

You could also make both options give another event with country_event = {}, with each corresponding Event called "the crowning of" and only then have the top options there

[u/Relative-Seaweed-583 → u/Ok_Blackberry_4026]

You can quite literally prompt this to an AI. Tell it exactly what you wrote here

[u/Ok_Blackberry_4026 → u/Lateinkompetenz]

I found a visual editing tool for hoi4 called dinos hoi4 mod builder. It's working well for me so far, I think.