I'm currently working on my bachelor thesis with texstudio. There is a tool integrated which is quite helpful for making improvements in my writing style. It is called "word repetition" and marks up words which are repeated within a small word distance. I want this tool to look up the a lager distance to improve my document but don't know where to find the advanced options.
The scope of the word repetition check is in terms of words, not sentences.
The settings for word repetition check is hidden behind the Advanced Options. In the Configure TeXstudio menu, check the bottom left box that says Show Advanced Options.
Under Language -> Internal Grammar check, you will find the options to increase/decrease the length of the scope of word repetition check.
You would want to increase the numbers for the first two boxes, in your case, I believe.

language->internal grammar check?Words between repetitionandLong range repetitioncount. (default is 3 and 10 respectively, I think). Take note theshow advanced optionscheckbox (bottom left of the options menu) must be checked.:)