You can make a new folder in the tree to the right where your other results are located.
I forget the name of the folder off the top of my head, and I don't currently have access to the software. You need to right click on the folder heading and then create a new folder. After you have the new folder all you have to do is right click on the name of your plot in the tree and then copy/paste to the new folder. Then when you run a new simulation from within the same project you won't loose this data.