I didn't know about this until I discovered it the other day, but I can already see its come in handy. If you use arrays of structures and have one in the NS3 debugger, you have to click on the plus sign to expand the array to look at the structure data, and if a structure has a structure in it, that's another plus sign to click deeper into the data structure, and so you clumsily click your way through your data structures. What works better, is to click in the debugger window and use the arrow keys to navigate through your structure. Hitting right arrow at any time opens the next level, left closes it, and then you can quickly scroll through many items briefly taking a look at the data by hitting right arrow, then left, down, right, then left, looking at each element without all the mouse wrangling. Perhaps this is already well known, and if so, disregard, but I have found it helps take the tedium out of watching variables in the debugger.