What about super-huge wormholes in intergalactic space? These could be truly immense and possibly useful for moving from one part of the universe to another, perhaps as a way of reaching distant galaxies, though it seems detecting them and actually utilizing them would be tricky. Still, not impossible, and if nothing else, they would be a scientifically fascinating thing to discover.
As far as my knowledge goes on wormholes they would require vast amounts of negative energy. Such energies in large deposits most likely don't exist and any forming wormholes would collapse in on themselves. Doesn't seem very realistic to include them in Space Engine.