This might be helpful
But another idea is to create a repeating group using List of Numbers plugin…you can calculate the number of items in your list of items, then set the List of Numbers to be +1…then create a repeating group that is for display. That r.g. will be displaying the list of numbers as a data source so you get the number of items in the list +1 as the total cells in the repeating group.
Then have another r.g. that is hidden in a popup that contains the list of items by using a datasource “do a search for items”…this will be what you use to count the number of items in the list. But also for showing those items in the r.g. that has the extra cell.
In the r.g. with extra cell need to have a group to display the items…use the datasource for the group as the hidden r.g. item number equal to current cells index…which should get you in cell index 2 item number 2 from the hidden popup. Then add another group that is displaying your message. Conditional formatting to be visible when current cell index is item list count + 1