I doubt we'll be able to create new supper abilities, I'd guess that is beyond the scope of any of the editors since a supper ability would need code to support it.
Well... given the nature of the Racial Tech Trees, it wouldn't be too hard to imagine being able to give a new "Super Ability" in the form of a unique, non-tradeable/stealable tech that gives some bonus that could normally be given via techs.
For instance, a race with No Super Ability has a tech called "Super Economists" in its tree that gives, say... +30 Economics. Give the tech a cost of 0 (or just assign it as a starting tech or both), and now they are Super Economists.
In the same way, you can technically modify the current Super Abilities.
Of course, this isn't exactly the most elegant way of doing things, but it would work. Granted, someone could "cheat" and take a normal super ability along side this pseudo-one, but, they were probably going to cheat anyway, no?