Defining a new SideSet in an Exodus file

Hello,

Is there any way I can define a sideset in a .e that contains simulation results?
I created my mesh in Trelis, then run my code.
Now I need to run another simulation from those results, but I need to define a new side set for a new boundary condition for my new simulation.

Is there any way I can do this using Trelis?
I mean, open a .e file and defines a new side set on that mesh?

Thanks!