Dear @Alice_Packard1, welcome to the community.
I just checked again, the trick is that you should temporary for from card view to table view, right click on the yellow marked area next to “not started” in the sample below. Then in “Arrange and manage groups” you will be able to"pin cards" that you want to show in case it’s empty, when your settings are ready, go back to the card view and all should work fine:
I think this is one of the best hidden features in Coda 