I was pleasantly surprised to see that "basic" breakback persists into New UX. This was particularly helpful on a board with two grids - one using years and another synched using quarters or months. Entering data by year in to a strategic input grid and then allowing it to be spread by quarters or months in the child grid is a great UX. Will be nice to see a fuller set of breakback features (display,hold,etc) implemented in future.
Thanks, @usman.zia . The use case here is capturing of data for strategic initiatives (building and consolidating business cases). Ease of use for rapid modelling is critical. Users can always fine-tune items by lower entry periods (quarters) after entering data by year. Since there are a significant number of lines to be entered, reducing the number of periods for entry is helpful.