How to convince the faculty search committee to select/short list me at a place where my research interests are already actively being pursued at?
That is essentially not something you can do. Whether or not a department wants an additional faculty member in an area is something the department needs to figure out. As I mention, "The research topics are extremely complicated" is something that every researcher can and will (correctly!) say about their own research area, and having another colleague in their area will help them as well. As a consequence, if you claim that hiring you will be good for the research group then that will likely not have much of an effect -- the search committee members will know that this is true for a hire in any area already represented in the department.

In practice, figuring out in which areas a department wants to hire is often a difficult and contentious process. Everyone wants more faculty in their own area. An outsider will not generally have a voice in this process, and so you trying to convince them of something that they need to figure out themselves seems to me like a futile thing. Focus on making your application look good by having lots of publications in good journals, writing proposals and getting them funded, etc. What you can do is point out that your research would have natural connections to researchers already in the department, and who this is.