Business & farm

Yes you can add notes in TurboTax CD/Download version. Select Forms in the top right corner, the scroll to select the form where you want to add supporting information. Not all fields will allow a supporting details entry, however some do.  Find the field where you want to add supporting details then right click to add.  In my example below it was added for the specific information printed by using the Dependent Wks in the list of forms on the left.

Supporting details can be good so that you have the notes you want to carry forward for future tax returns.