Hi 3image, currently booleans will merge faces together in 2 cases - if they are coplanar planes, or if they share the same full underlying surface. There isn't currently any mechanism in the booleans to merge together 2 extrusions into a single face but that is something that I would like to look into adding in the future. It is possible to manually merge those types of things by deleting the faces and making a longer extrusion though.

- Michael