Hi rockie-rocafort, I read the product code for you and it seems the logic for the filtering is hard coded into the query in com.adobe.cq.projects.impl.ProjectStorageProvider. So in order to override filtering you would need to modify these files:
/libs/cq/gui/components/projects/admin/datasource/projectsdatasource/projectsdatasource.jsp
/libs/cq/gui/components/projects/admin/clientlibs/projects/js/graph.toggle.js
Create a filtering button similar to this one for your additional filtering:
/libs/cq/core/content/projects/jcr:content/actions/secondary/filterActiveProjects