I always understood "omnipotent" as "can set the state of the universe to anything" (like someone pausing a simulation to make some changes).

This might be insufficient, if inhabitants of the universe care about the facts following from the original definition of the universe (which facts normally can't be controlled by changing the state of a simulation), and not about the state of any particular simulation (which they won't even be able to perceive without special equipment that responds to facts about the simulation).