For those MXDs that have multiple data frames, it would be nice to see which data frame map elements like scale bar, legend and north arrow are associated with. Frequently, I inherit maps other folks have worked on. In it, there will be several data frames, including an inset map. I find I have to change the scale and watch the scale bar to see when it changes units to determine which data frame the scale bar it belongs to. It would be great to see this on the Properties window like the example below.