It's nice to have your newly created and optimized plan appear alongside the original plan, so that you can compare:

 

 

 

But sometimes, you may want to optimize in place, that is, don't create a new column just revise the original plan.  The choice is here, on the Optimize dialog:

 

 

A particular use for optimizing in place is when you want to conduct a separate optimization for different parts of the same plan (click there to read more), such as to refine the general market and the Spanish-language portions of a plan separately.