I don't think there is a magical way to search across generations horizontally, no, row fashion. Generations are built columnar fashion. To locate a 3rd cousin there has to have been the vertical columnar line of descent from a great-great-grandfather, for instance.
You and your 3rd cousins would all share a line of descent. But you need a key word or key words -- NOUNS -- to identify who those 3rd cousins are, for instance, and that would name at the least, a birth year, a location lived in, a parent's name for instance, or perhaps a snippet of DNA by all its ID code. Whether they are PM at WIkiTree is another whole thing.
Whatever else you yourself will have to invest time and energy and effort into directing any search, selecting nouns, refining the terms used in the search, collecting and organizing and storing the results of a search. You cannot escape that.