This is idea is essentially to provide the ability/option to drill down in BOARD the same way that it works in Excel with the office Add-in.
When drilling down on a layout in Excel it does it what I call 'in-line', in that it expands/inserts down to show the detail in line. It doesn't have a drill pop-up like in native BOARD client.
This idea is to enable the same function in native BOARD, so that rather than a drill-down pop-up, the dataview would expand down and show the relevant rows in-line in the same dataview. The user could then click the drill-arrow again to 'un-drill'
It would be similar in behaviour to a collapse/expand but would offer a more tidy display without all the '+' buttons and 'group by' lines, which I don't believe are appropriate for financial reports (PL/BS/CF). It relates somewhat to another idea on here (Etienne's Idea) in that it would also allow the use of Rules at the parent level yet also enabling display (through drilling) of child level detail.