At the point of 1.12 and backwards (before the new command system) when using the /setblock command you could easily get the coordinates of the block you were looking at by pressing [tab] in the requred areas in the command. This is also the case for the new /fill command now. This is no longer in the newer snapshot with the new command system. I haven't tested it out on other commands than fill and setblock, but believe this should be fixed.