It's an extra key press, but ctrl-c copies the current line if there's no selection; then ctrl-v pastes it in front of the next line. Alt-click adds a cursor.

It's an extra key press, but ctrl-c copies the current line if there's no selection; then ctrl-v pastes it in front of the next line. Alt-click adds a cursor. :) Also, alt-up/down adds cursors above or below the current cursors.