Breakback functionality allows you to change the numbers which otherwise you will not be able to change. For example changing the numbers in Q1 and anaplan re allocates the numbers for all the 3 months of Q1. Let's say if we want to copy paste the numbers in all the three months of Q1 as well as for Q1 itself ( making the count as 4) it will throw an error in Classic UX
Numbers I wanted to copy paste
Jan = 1300
Feb = 1230
Mar = 1430
Q1 = 1540
Error is valid because it doesn't make any sense that you input values for all 4 which doesn't tie up at all. (Q1 is not summing up with Jan, Feb & Mar)
In NUX: these type of alerts are missing.Making you think that the copy paste doesn't work
Now, In order to validate it here is what I have done:
Case 1: I have copy pasted just three values and below is the result. (Q1 being an input because it is breakback enabled cell).
Case 2: Let's try to input all four but Q1 matches exactly with the summation of Jan, Feb & Mar it copy pastes it without any issue. There is a small lag but it copy pastes successfully.
Case 3: Finally I tried to Copy paste all the 4 numbers where my Q1 was not matching with Jan, Feb & Mar summation. it doesn't do anything, because it doesn't make any sense if you input all 4 when you parent is not matching with its descendents