To manually enter an amount on Schedule 3 Line 13z, you will have to use Forms mode.
Click on Forms
When in Forms mode, on the left side of the screen is a list of all the forms, schedules and worksheets for your tax return. At the top of list should be the 1040/1040SR Worksheet. Click on 1040/1040SR Wks to open the worksheet. With the worksheet opened, scroll down to the Schedule 3 section and on Line 13z enter the description and the amount of the Other Nonrefundable Credit.
