When clicking properties of the mount point of a device the window shows a graph with the usage of the disk and the space left, but when doing it in a sub folder doesn't appear any graph. I know that the relevant use of the graph is in the mount point, but, if a graph for each folder is made being the same graph but with a green (for example) sector showing the space of the folder relative to the disk size inside the yellow sector (total disk usage) could be very useful, at least for me.