Here's another one of those right-click tips again.

If you right-click on the command line, a short pop up menu appears.  The second listing, Paste To CmdLine, is usually grayed out unless some text is highlighted.  This command will Copy and Paste the highlighted text back to the command line.  This really helps when you have a long string of digits to enter for the X, Y, Z coordinates that have been listed previously in the command line history for 3D entities or points.