Is an expense in Today's Dollars that starts at retirement going to be the inflation-adjusted amount?

If you model the starting amount for something in Today’s Currency, then yes, it will start at an inflation-adjusted amount.

And if you want subsequent years to continue to be adjusted for inflation after that point, that’s where the “Change Over Time” section comes into play.

To build an intuition for how this works, try modeling a test expense or income stream, and then toggling back-and-forth between visualizing results in Today’s Currency and Actual Currency (selector in upper-right of chart on the Plan tab), and inspecting the corresponding items in the yearly summary pane. The Cash-Flow tab can also be helpful for this.