Patching .lng Files
The .lng file stores various text which is called upon by the .csv files for things such as names and descriptions. Many modifications to the game will require patching the .lnf file.
In the picture below, we take a look at players.csv, and see that the values in the desc1890 column, specifically Korea in this example, don't actually give a description. This is because they are calling text from the .lng file.
When looking at the English.lng file in the picture below, we see the exact same format as in players.csv. This is where the text data seen in game is stored in order to reduce the clutter in the .csv files. In this specific case, the country description for Korea in 1890 in DIP Extended is highlighted, just as it was in players.csv.
The .lng files in the Mods folder overrides the text used in vanilla, so renaming something is a simple matter of knowing the code for the text you want to change and following the pattern shown in the file. The same applies when creating new text files, just remember to reference the text everywhere it is needed.