A user at en.wp has noted the lack of a tool to set superscript means that the article [[Spiral Dynamics]] cannot be completely edited in VE.
The ability to set superscript and subscript are essential features for writing about many articles in the science, maths and technology fields, so it should be a core competence of the VisualEditor rather than a low-priority enhancement.
As explained elsewhere, this is trivial to do but would make the toolbar (even more) unwieldy for all users, and so I de-prioritised it whilst waiting for a way to have lots of these icons available without filling everyone's screens with buttons most of them don't want to touch.
We're working right now on a first draft which we think will help with the clutter, at which point making these tools is a work of minutes.
Now merged into master; will be deployed (as experimental) in the next push (so will be available on MediaWiki.org) - we will make this available to production wikis next week when we re-work the toolbar.