The white crosshairs diagram that appears when the Select Textures option is selected from the Edit window is very useful. It is a quick and easy visual way to align textures across multiple prims (such as a complex brick pattern across an exterior wall). Simply set the texture repeat values the same for the adjacent prims, then adjust the offsets until the white crosshair overlay lines up across the edges of the adjacent prims.
However, under normal circumstances, this overlay cannot be seen on more than one prim at a time. Yes, selecting the option on a linked set, or selecting multiple unlinked prims for edit at once, will display the overlay crosshairs, but they disappear the moment you select a single face for texture edits.
I propose a debug menu toggle to display these crosshairs on ALL surfaces for extended periods. Perhaps a more detailed texture edit crosshair/overlay for aligning textures over larger surfaces would also be in order- maybe even a numbered grid on the surface indicating the X and Y offset. This could be an extremely useful tool. See the picture below for an example of the overlay lined up and spread across multiple prims.