palmtree – Sorry about the delayed reply. At present, the filter gets changed to the chosen categories only if you specify one or more categories in the Taxonomies field of Build Query window. The functionality is there but limited to Taxonomies field since it is hard for us to read custom query arguments specified in Additional field with its innumerable possibilities.
And also if you do specify the taxonomy argument, the build query function of the siteorigin page builder does not return the elements that belong to child taxonomy terms. So, the query results output would be just those posts which belong to category 5 and no posts which belong to child categories is returned by the siteorigin query builder. You can verify the same by the red colored number of posts that gets displayed in the Build Posts Query button.
Hence, even if we built a filter which takes into account child categories, it would not be useful since no posts from the child categories would be populated. The cat=5 does the same and returns no child category posts.