Using Prior year's filing to do what if scenarios to estimate/plan next year's taxes?

I do my taxes using TurboTax and am wondering if after filing I save a second copy of the return under another name i.e.".......whatif..........".  Would this work to then use to run what if scenarios say for things like what would the tax impact be if I recognized a capital gain of $X or I started to claim Social Security or IRA distributions etc etc?