I looked up how to change the language that Steam is spell checking when I write in forum post etc.
I needed to change the "dictionaries" line inside the UserPref.json to add english as the language to spell check.
Sure, I did that and saved the file, still kept the file open and restarted steam, went to a forum post to write something and the red lines are all there again, spell checking only my own language (sv).
I still had the .json open, as I mentioned but not in focus, and it still had the "en-us" that I added so I clicked on it to have it in focus and it instantly changed back to just "sv".

Edit: I guess steam detects my system language, but Steam it self is in english, so it really should spell check the language Steam is using.

So, how do I keep the change that I did in the .json file so that steam can spell check my english writing?