@mwjames on SMW's issue tracker writes:
While trying to consolidate our special pages into one coherent section it became clear that collecting all pages into one section creates some inconsistencies where users cannot clearly distinguish pages (by topic, or interest) on a subsection level (as shown below). We would require a tiny change to SpecialSpecialpages in MW-core to allow us to define a subsection using / as separator in the group name.
Mock-up:
Unless someone beats me to it, I'll put something in Gerrit tomorrow.