Despite the other replies, at only 1% of the speed of light you could set up a reasonably similar situation. The deviations between Newton and Einstein here would be significant if you were trying to literally plot an orbit for your visiting spaceship (and why the bloody hell would you want to do that?!), but not if you just want to watch two high mass objects dance around each other really quickly for a bit.
My question would be more about whether the simulation has sufficient granularity to avoid the star flying away due to the time step being too large, rather than concerns about relativity. And of course Universe Sandbox won't be simulating the black hole tearing away bits of the star, or at least, so I'd presume.
If I recall my physics correctly the most important thing it would miss is the orbital energy of the start slowly being radiated away as gravity waves and the star eventually being swallowed by the black hole.
My question would be more about whether the simulation has sufficient granularity to avoid the star flying away due to the time step being too large, rather than concerns about relativity. And of course Universe Sandbox won't be simulating the black hole tearing away bits of the star, or at least, so I'd presume.