One slightly unpleasant feature of LanguageTool with Texstudio is that new words are a little harder to add to the dictionary than when using Texstudio’s native spellcheck.
The good part of having to add words through LanguageTool is that words you add are, well, actually added to the dictionary, whereas adding words to Texstudio’s native dictionary is — in my experience — unstable (I’ve had to add the same words multiple time in many occasions, in particular after updates).
For explanation on how to add words to LanguageTool’s spell check, once again see the very good documentation on LanguageTool’s website at http://wiki.languagetool.org/hunspell-support#toc0.
I will try to keep an updated list of words I added here. The list might be of some use in particular to those working in a field related to microeconomics theory.