Custom subtitles?

[Abion47]

There's a Korean language patch on the Steam Workshop that I believe does a total translation including subtitles. It might be worth looking into.

As for the Swedish letters, å, ä and ö correspond to the Unicode character codes [00E5] [00E4], and [00F6], respectively. The lang files are basically XML, so you can try the escape sequences "å", "&#x00E4", and "ö" for those characters. (I'm not at a place where I can try this myself at the moment, but as we've seen with some of the FG lang files, they don't appear to adhere 100% to the XML specification, so it's possible you could also just use the characters themselves directly.)