The form itself has lines for 3 charities (and another 3, for donations made in 2021 that apply to 2020).  Glad I don't use ProConnect.  

In ProConnect Tax, whenever you see an entry being made on a tab and that tab has a + next to it, that's indication to you that to add a new entry, you just need to click on the + sign.  The flip side of the coin is that, to delete an entry, you just need to click on the x in the right corner of that particular tab.

The area I was asking about AZ - Other Tax Credits - 321 
Did not have the expected + on the tab for additional credits under 321

AHA! i was expecting it are the row level - thanks for your help