Boxes 18 &19 (W2) each have two rows with different amounts. Box 20 has two rows w/ the same location. TurboTax thinks they're duplicate rows. Can I add the 2 rows?

Boxes 18, 19, and 20 contain local income tax information and the locality.  If the locality is the same in each, you can add the amounts in each line and make one entry for boxes 18, 19, and 20.

Refer to the answer in this post by TurboTax Expert for more information.

Refer to the TurboTax article What is a W-2 Form? for explanations of what's in the boxes.