Enable tech research [OWB]

To start, you must first be able to edit your save files. By default the game saves them as binaries, hence this must be changed before anything else can be done.

Do not worry, this is super simple - just go to the HOI4 folder in your "Documents" folder and edit the "settings.txt" file, where you will find the line "save_as_binary=yes" which you need to change to "save_as_binary=no".

In case you need it, below should be the filepath to find the settings file, simply replace [username] with your windows profile username:

C:\Users\[username]\Documents\Paradox Interactive\Hearts of Iron IV

I highly reccommend using a text editor like Notepad++ for doing all this

Due to the way the mod seems to work, simply adding in the line that enables technology level research is not enough. I spent the good part of an hour (why I decided to write a guide) figuring out why and what needs to change for it to truly enable.

1. First, open up your save file and search for "game_rules={". This will be an empty block if you've not touched any gamerules at new game creation.
   
2. Now, we'll populate this by adding " Tech_advancement_gamerule="enabled" " between the { }
   
3. And lastly, you will have to find your unlocked technologies and add a technology, now this will be broken down into smaller chunks to make things easier. Don't you love ordered lists? :)
   1. Find your nation tag, this seems to be a 3 letter string and can be found at the very top of your save file. In my case it's "ARR" due to me playing as Arroyo.
      
      
   2. Search for this, with your tag inserted into "[tag]":
      
      technology={ override_icons_tag="[tag]"
      
      
   3. Insert the following block of code after the line "technologies={":
      
      blocked_tech_level={ level=1 research_points=60 date="2275.1.1.12" }
      

There you go! Save the document, load the savegame and Bob's your uncle. You will now have the ability to progress tech levels.

You can use the first half of this guide to essentially add any gamerule to an in-progress game, but I do not know how this will affect your save or if it would at all work for any of the gamerules. As you can likely tell by the guide, it's not as easy as

1. Get gamerule name
   
2. Paste gamerule name under "game_rules={"

So go about it at your own risk.

The easiest way to get the game rule names is to start a new game, click custom game rules, enable everything and save that as a preset. This will save a text file to a folder in the same binary called "game rules" with whatever name you assigned it, from which you can copy and paste them however you please.